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Digitized by the Internet Archive
in 2011 with funding from
The Library of Congress

http://www.archive.org/details/appliedanatomykiOObowe

THE PHYSICAL EDUCATION SERIES

Edited by R. TAIT McKENZIE, B.A, M.D., M.P.E.

MAJOR, ROYAL ARMY MEDICAL CORPS
'ROFESSOR OF PHYSICAL EDUCATION AND PHYSICAL THERAPY, UNIVERSITY OF PENNSYLVANIA

PHILADELPHIA

APPLIED ANATOMY AND
KINESIOLOGY

THE MECHANISM OF MUSCULAR MOVEMENT

WILBUR PARDON BOWEN, M.S.

PROFESSOR OF PHYSICAL EDUCATION, MICHIGAN STATE NORMAL COLLEGE. YPSILANTI, MICHIGAN

SECOND EDITION, THOROUGHLY REVISED

ILLUSTRATED WITH 197 ENGRAVINGS

LEA & FEBIGER

PHILADELPHIA AND NEW YORK
1919

' 1*1

LEA & FEBIGER

1919

JON 25 1919

©CI.A530021

AUTHOR'S PREFACE.

Kinesiology is the science of bodily movement. It includes a
study of the principal types of muscular exercise, with inquiry as to
how they are. performed, how they react on the body, and their
relation to the problems of bodily development, bodily efficiency,
and the prevention and cure of certain defects and deformities. To
make such a study it is necessary to analyze complex movements
into their simplest elements, note carefully what bones, joints, and
muscles are involved, what part each muscle has in the work, and
under what mechanical conditions its work is done. There are
two main reasons for our interest in the subject.

The first of these reasons which may be mentioned is the scien-
tific one. All complex problems challenge our ability and stimu-
late a desire to master them. People are especially interested in
the use of force to accomplish results, and show wonder and curi-
osity whenever they see a printing press, a steam thresher, a dynamo,
or a locomotive in action. Interest in such machines is largely due
to their complexity, which hides the manner of their action and
stimulates curiosity as to how they work. The human body is a
machine more complex and adaptable to a greater variety of work
than any other to be found in the whole range of nature and inven-
tion. Machines have been built that are larger than the body and
that are capable of greater speed, but no machine has been made
nor is likely to be made that can walk, swim, climb, throw, lift, or
strike, as occasion demands, although the body is considered very
defective unless it can do all these things and many more. When
we think of the really complex and difficult feats the body can per-
form, as illustrated by the performances of ball players, acrobats,
jugglers, etc., it is plain that the body is in a class by itself as a mar-
vellous piece of machinery. This is why no spectacles draw such
crowds nor create such enthusiasm as exhibitions of human skill;

IV AUTHOR'S PREFACE

it is also the reason why there are no problems more fascinating to
the student of science than those of Kinesiology.

The second reason for our interest in Kinesiology is practical.
The work done by the machine reacts on the machine, modifying
its development and the efficiency of its action. The maxim of
biologists that "Function determines structure" is nowhere more
true or more important than in muscular work. Although heredity
has some part in it, nevertheless what we are depends largely on what
we have done. The difference in physique between the athlete and
the bookkeeper is in great measure the result of different kinds and
degrees of activity. The reaction of the work upon the body is not
only developmental but mechanical, for it influences the posture of
the joints and the shape of the bones. Those who examine large
numbers of men soon learn to tell almost immediately from the
look of a man what his previous occupation has been. It follows
that anyone who wishes to keep his own bodily machinery up to a
fair grade of efficiency will do well to study Kinesiology, while those
who plan to direct the bodily activities of others with a view to
development and health need to have its main principles constantly
in mind.

The study of Kinesiology brings us into a fascinating borderland
lying between- the fields of several sciences. We must first of all
study something of anatomy, because we need to be very familiar
with the size, structure, and location of the muscles, the exact
points where they join the bones that act as levers, the nature of
the joints on which they act, etc. ; even those who have studied
anatomy for other purposes can afford to review briefly the points
of most importance here. We must note the way muscles do their
work, which brings us into the field of physiology. A brief excur-
sion into the field of mechanics is necessary to make us familiar
with the problems of leverage and of the composition and resolution
of forces. Finally, in studying the causes and conditions of certain
bodily defects we touch upon the domain of pathology and thera-
peutics; and all the time we are close to the field of personal hygiene.

The real test of the mastery of this subject by the student is the
ability to analyze and solve problems of Kinesiology that occur
daily in the practice of the physician and the physical educator.
Even if the main problems, as stated and explained here, are learned

AUTHOR'S PREFACE v

thoroughly, they occur in actual practice in such infinite variety
and with such constant change of form that no one can deal with
them effectively without the exercise of some ingenuity. Many
physicians and teachers are so little versed in Kinesiology that they
never see many of these problems that are constantly presenting
themselves, to say nothing of solving them, much to the misfortune
of their patients and pupils. Many cases are so complex and diffi-
cult that they should be referred at once to specialists; a fairly
efficient student of Kinesiology can determine such cases at once.

W. P. B.

Ypsilanti, Michigan.

EDITOR'S PREFACE.

The first experience of most medical students in the dissecting
room is one of disappointment at the apparently unfavorable
position in which the muscles appear to be placed for the work
that they are supposed to do, and it is only after more careful
study that the intricate and exquisite adjustment of position to
action is discovered. Increased knowledge stimulates apprecia-
tion of this intricacy until the student of Kinesiology will cheer-
fully argue all night about the real action of the biceps, already
overworked as an illustration, but whose action is seldom correctly
stated, or on the less obtrusive intercostals the functions of which
have divided scholars into two hostile camps for the last hundred
years.

The understanding of accurate muscular action is most vague,
even in the minds of otherwise well-trained physicians, and I
have seen committees of learned doctors absolutely at a loss to
explain how a frail little woman could resist with ease the united
strength of four strong men or how she could apparently change
her weight at will. These wonderful feats which seem out of all
proportion to her visible power are but examples of muscular
action diverted to deceive those who are ignorant of the subject
treated in this book, and the fact that so few detect them illus-
trates the density of the fog that in most minds envelops the
simplest problems of muscular action.

The less theatrical application of these principles is employed
by the American Posture League, in designing clothing, furniture,
machinery and even car seats so that the mechanical construction
of the body may be respected and not deformed. Its committees
are doing much by the study of the principles discussed by the
author to slacken the constant and insidious strain of nerve, muscle,
ligament and bone that pulls down the efficiency of both young
and old.

Vlll EDITOR'S PREFACE

But there is still more urgent need of knowledge on this subject
at the present time.

During and after the great war, behind every battle front, in
hospitals and camps, tens of thousands of crippled soldiers have
been brought back to strength and usefulness, largely by the
reeducation of muscular movements.

In undertaking the editorship of this physical education series, of
which this is rightly the first volume, I see the possibility of doing
a real service to education and medicine by helping to place physical
education on the plane that its importance and dignity demand.

Both by training and inclination, Mr. Bowen is especially well
adapted to write the initial volume; a practical teacher and a close
student of applied anatomy for many years, his pen has not been
idle, and in the following pages he has gathered the fruits of his
ripened experience and mature judgment for the large audience
that awaits him.

R. Tait McKenzie, M.D.,
Editor.

CONTENTS.

PART I.

GENERAL PRINCIPLES.

CHAPTER I.

Muscular Structure and Action.
Methods of Studying Muscular Action .28

CHAPTER II.
The Bones as Levers 32

CHAPTER III.

Muscular Control.

Neurones 40

The Nervous System . • 42

Motor Neurones . 45

Sensory Neurones 46

Association Neurones 49

Stimulation and Inhibition 53

Normal Muscular Control 55

PART ir.

THE UPPER LIMB.

CHAPTER IV.

Movements of the Shoulder Girdle.

Trapezius 62

Levator 68

Rhomboid 70

X CONTENTS

Serratus Magnus 71

Pectoralis Minor 75

Subclavius 76

Posture of the Shoulders 77

CHAPTER V.

Movements op the Shouldek-joint.

Deltoid 84

•Supraspinatus , 88

Pectoralis Major -. 88

Coracobrachialis 91

Latissimus 93

Teres Major 95

Infraspinatus and Teres Minor 96

Subscapularis 97

The Fundamental Movements of the Arm 97

Elevation of the Arm 98

Depression of the Arm - 105

Extension of the Shoulder-joint 107

Flexion of the Shoulder-joint 107

Gymnastic Movements 108

CHAPTER VI.

Movements op Elbow, Forearm, Wrist and Hand.

Triceps 117

Biceps 119

Brachioradialis 122

Brachialis . . ; 123

Pronator Teres 123

Pronator Quadratus 124

Supinator 124

Fundamental Movements 126

Gymnastic Movements 129

Games and Sports 132

CHAPTER VII.

Movements op the Hand.

Muscles Acting on the Wrist-joint 139

Flexor Carpi Radialis 139

Palmaris Longus 140

Flexor Carpi Ulnaris 140

Extensor Carpi Radialis Longus . . .140

CONTENTS xi

Extensor Carpi Radialis Brevis 140

Extensor Carpi Ulnaris 141

Muscles Moving the Fingers 142

Flexor Sublimis Digitorum 142

Flexor Profundus Digitorum 142

Extensor Communis Digitorum 144

The Lumbricales 147

The Dorsal Interossei 147

The Palmar Interossei 147

Muscles Moving the Thumb 150

Extensor Longus Pollicis . 150

Extensor Brevis Pollicis 150

Extensor Ossis Metacarpi Pollicis 150

Flexor Longus Pollicis 151

Flexor Brevis Pollicis 151

Flexor Ossis Metacarpi Pollicis . 152

Abductor Pollicis 153

Adductor Pollicis 153

Fundamental Movements of the Hand 154

PART III.

THE LOWER LIMB.

CHAPTER VIII.

Movements of the Hip-joint.

Psoas 158

Iliacus 160

Sartorius 160

Rectus Femoris 161

Pectineus 162

Tensor 163

Gluteus Maximus 163

Biceps 166

Semitendinosus 166

Semimembranosus 167

Gluteus Medius 168

Gluteus Minimus . 168

Adductor Gracilis 170

Adductor Longus 170

Adductor Brevis 170

Adductor Magnus 171

The Six Outward Rotators 172

Xll CONTENTS

CHAPTER IX.

Movements of the Knee-joint.

Vastus Externus 178

Vastus Internus 179

Vastus Intermedius 179

CHAPTER X.

Movements op the Foot.

Tibialis Anterior 190

Extensor Longus Digitorum 191

Extensor Proprius Hallucis 191

Gastrocnemius 192

Soleus 192

Peroneus Longus '. 194

Tibialis Posterior 196

Peroneus Brevis 197

Defects of the Foot 198

Fundamental Movements of the Lower Limb 201

PART IV.
THE TRUNK.

CHAPTER XL

Movements of the Spinal Column.

Rectus Abdominis 211

External Oblique 212

Internal Oblique 212

Splenius 213

Erector Spinee ' 214

The Oblique Extensors 216

Quadratus Lumborum 217

Fundamental Movements 218

Gymnastic Movements - 220

CHAPTER XII.

Breathing.

External Intercostals - . . . 228

Internal Intercostals 228

CONTENTS xili

The Diaphragm 232

Sternocleidomastoid 234

Scaleni 235

Serratus Posticus Superior 236

Transversalis 237

Serratus Posticus Inferior . . 238

CHAPTER XIII.

The Upright Position.
Defects of Posture 254

PART V.

GENERAL KINESIOLOGY.
CHAPTER XIV.

Team Work among Muscles 267

CHAPTER XV.

Gymnastic Movements 278

CHAPTER XVI.
Plays, Games and Sports 300

CHAPTER XVII.

Industrial Occupations 318

APPLIED ANATOMY AND KINESIOLOGY.

PART I.

GENERAL PRINCIPLES.

CHAPTER I.
MUSCULAR STRUCTURE AND ACTION.

The muscles are the immediate source of all the energy the body
can use to move itself and other things. Originally derived from
the sun, this energy is caught and stored by plants in latent form
in the food materials they produce. These are eaten, digested,
absorbed, and then built up anew into the structure of the muscles,
where the energy so long imprisoned can be set free to do work.
With the long series of chemical changes involved in this storage
of energy, its preparation, its rebuilding into muscle tissue, and its
final dissolution during muscular action we are not concerned here.
The way muscles use the energy, however, when it is set free, is
related to their internal structure, and something of this we must
now observe.

The entire muscular system includes nearly 200 pairs of muscles,
but only about 75 pairs are involved in the general posture and
movement of the body, and our study will be limited to this
number. The others are smaller and are concerned with such
minute mechanisms as those controlling the voice, facial ex-
pression, and the act of swallowing. The muscles, like the bones,
are of various sizes and shapes, every one of the 75 pairs being
recognizable by its size and form. Some are in flat sheets, like the
trapezius (Fig. 30) and the transversalis (Fig. 142) ; some are long
and slender, like the sartorius (Fig. 92) and the peroneus longus
(Fig. 113) ; some are spindle-shaped, like the biceps (Fig. 50) and the
pronator teres (Fig. 70) ; most of them are of such irregular shape
2

MUSCULAR STRUCTURE AND ACTION

that a classification based on form is not practicable. Each pair
is named, some of the names indicating the form, as in the case of
the rhomboid and teres major; some indicating action, as the levator
and the supinator; some indicating location, as intercostal and

Fig. 1. — Muscle magnified, showing the muscle fibers and the nerve fibers. (Gray.)

supraspinatus; a few are named from the bones they join, as the
brachioradialis and the sternomastoid.

Each muscle is composed of thread-like fibers, the number in a
muscle varying from a few hundred to several hundred thousand.
Each muscle fiber is an independent unit, having its own individual
connection with the nervous system by a nerve fiber, through which

Fig. 2 — Fibers of muscle and tendon, showing striping and nuclei in the muscle
fibers and a sensory nerve ending in the tendon. (Klein.)

it receives the influences that control its action. The muscle
fibers vary in length from 200 to 1000 times their width, and lie
close together, parallel to one another, with minute spaces between
for the lymph on which they feed and into which they pour their

MUSCULAR STRUCTURE AND ACTION 19

waste products. The fibers are too small to be seen readily with
the unaided eye; they can be so stained that when seen through
a microscope both the muscle and nerve fibers are visible. Notice
in Fig. 1 the parallel muscle fibers and the smaller and more
darkly stained nerve fibers (a) going to them and terminating in
the motor endings (t).

Fig. 2 shows nuclei and the junction of muscle and tendon. The
muscle fibers are shown below and the tendon above. The muscle
fibers are seen to be crossed laterally by alternate bands of dark
and light, and in each of them are seen the dark oblong nuclei
irregularly placed. Each fiber is really a cylindrical mass of jelly-
like protoplasm enclosed in a thin and trans-
parent membrane called the sarcolemma.
The sarcolemma keeps the protoplasm of
the different fibers from merging into a
single mass of jelly and isolates each one
from all the rest, so that they can act as
separate units.

A portion of one muscle fiber, highly
magnified, is shown in Fig. 3. Notice that
here we are observing the finer structure of
a single muscle fiber, not a muscle. Fine
threads running lengthwise of the fiber have
on them certain enlargements, alternately
spherical and cylindrical. The fine threads
are called fibrils, and the clear space between
them is filled with a semiliquid substance
called sarcoplasm. It is readily seen that
the enlargements on the fibrils, regularly
placed, are what give the striped appear-
ance of muscle fibers under lower magnifi- . F\°- 3-~F°^onuoih,a

. it ii ii • i single muscle fiber highly

Cation. It IS now believed that all quick magnified. (Gerrish.)

action of muscles is performed by the fibrils,

while slower changes in tension and condition are due to the sarco-
plasm. In the arrangement of fibers into a muscle they are usually
grouped into bundles, each bundle having a sheath, and then the
bundles are bound together by the sheath of the muscle. The
fibers of many muscles are joined directly to the bones, but more
often there is a strip of flexible tissue called a tendon (Fig. 2), to
which the fibers join and which connects them with the bone.
Each fiber is attached by its sarcolemma, and tendons are in reality
formed by the fusion of all the sarcolemmas and sheaths of bundles
with the sheath of the muscle.

Muscular work is done by a change in the form of the muscle
called contraction, which includes a shortening and bulging out

20 MUSCULAR STRUCTURE AND ACTION

sidewise. A relaxed muscle exerts a slight pull on its attachments
because of its elasticity, but when it contracts it pulls with more
force. The contraction is due to the shortening of the separate
fibers, and each fiber as it shortens swells out laterally, stretching
its sarcolemma and the other sheaths surrounding it and thus
making the muscle feel harder to the touch than when relaxed.
This hardening of muscles as they contract serves as a convenient
test of muscular action, since it enables one to tell whether a cer-
tain muscle is taking part in a movement or whether it is idle.

The lateral swelling of a muscle in contraction may be used to
exert force, as is easily shown by tying a band of cloth about the
upper arm tightly and then forcibly bending the elbow. The
muscles that bend the elbow swell out as they shorten and press
out strongly on the band. Professional "strong men" often exhibit
their great power in this way, breaking ropes and log-chains drawn
tightly around the arm by a sudden bend of the elbow. Such a
way of doing muscular work, however, is no more than a curious
novelty; the bodily machinery is made to work by the pull of the
muscles on the bones to which they are joined and its structure is
developed on that plan. The lateral enlargement has this practical
importance, that all the force used in stretching sheaths, clothing,
or anything else that resists the free swelling of the muscles is so
much force wasted. There will always be a small loss due to this
cause, but each practice of an exercise diminishes it by making
the sheaths more distensible from the repeated stretching they
receive.

When a muscle contracts strongly it is apt to move both of the
bones to which it is attached, but to simplify the problem it is
usually assumed that the bone moving least is stationary. ' The
point where the muscle joins the stationary bone is called the
origin of the muscle, and its point of junction with the moving
bone is called its insertion. Evidently the insertion is the place
where the force is applied to the moving lever, and the distance
from the insertion to the joint which serves as the axis of movement
is the force-arm of the lever. Now it frequently happens in mus-
cular exercise that the bone that acts as a lever in one exercise is
stationary in another; for example, when one lies on his back and
then lifts his feet the trunk is stationary and the lower limbs are
levers, but when from the same position on the back he rises to
sitting posture the limbs are stationary and the trunk is the lever.
The same muscles do the work in the two cases, and it is evident
that origins and insertions are reversed when the exercise is changed.
The question as to which end of a muscle is origin and which is
insertion depends therefore on the movement made. Although
this is a matter of much importance in kinesiology, we shall for the

MUSCULAR STRUCTURE AND ACTION 21

sake of clearness of description follow the custom of anatomists
and call the end nearer the center of the body the origin. The true
origin and insertion can be told with ease when any mechanical
problem is involved.

The term "muscular tone" is frequently used in speaking of
muscles and so needs explanation. Everyone is aware of the fact
that we can contract a muscle at will to any desired degree of force
up to its full strength and then can relax it at will down to any
desired degree until complete relaxation is reached ; in other words,
instead of simply contraction and relaxation there are many possible
grades of condition between the two. It can also be observed,
although it is not so easy to notice, that there are different degrees
of relaxation when we consider the muscles at rest. For example,
if we feel of our muscles during or soon after a time of great excite-
ment, such as a ball game or a thrilling play at the theater, we find
them harder than usual, and further observation will show that
we are less able than usual to keep from making all sorts of bodily
movements, including talking, and that there is a feeling of tense-
ness in the muscles. After a night of good rest the tenseness and
hardness are gone. These changes in the tension of muscles when
they are not in ordinary contraction are called changes of "tone."
They are caused by changes in the condition of the nervous system
which are communicated to the muscles through the nerve fibers
going to them. Muscular tone is greatest during excitement, less
when one is quiet, still less when asleep; it is reduced still further
by the action of anesthetics and most of all by paralysis or sever-
ing of the nerve fibers. A very high degree of tone shades off imper-
ceptibly into mild contraction, as illustrated by shivering and by
the tendency to act when excited.

Muscles that are much used are apt to have more tone than those
used less; when this is the case between two antagonists the posi-
tion of the joint upon which they act is apt to be out of normal
position because of the greater tension of the one most used. For
example, many women use the extensors of elbow so little and work
with arms in front of the chest so much that their elbows are in
a habitual posture of half-flexion. Habitual posture of the body
depends much on muscular tone, and correction of posture is secured
by improving the tone of one muscle and stretching its antagonist
by the same exercise. Such exeicises are more efficient before the
tissues are matured by age.

The amount of work done by a contracting muscle is a combina-
tion of two elements of equal importance: the amount of force
used and the distance or extent of movement. Stated mathemati-
cally, the amount of work is the product of the force by the dis-
tance (W = F X D)> One unit of work is the amount involved in

22 MUSCULAR STRUCTURE AND ACTION

exerting one unit of force through one unit of space, so that we
measure work in gram-centimeters, foot-pounds, kilogram-meters,
foot-tons, or car-miles, according to the units of force and distance
employed.

In this connection it is important to notice two facts in the
working of muscles : first, that the force a muscle can exert depends
on the number and size of its fibers; second, that the extent through
which it can contract depends on the length of its fibers. It follows
from the first that the strength of muscles is proportional to their
cross-section, with the understanding that this cross-section is
taken at right angles to the fibers and includes all of them; the
second is related to the fact that a muscle fiber can contract to
half its full length. It has been found that human muscle in good
condition can exert a force of 6 kilograms per square centimeter
of cross-section, which is practically the same as 85 pounds to the
square inch. A muscle that has 8 square inches of cross-section
and fibers 6 inches long should therefore do 170 foot-pounds of
work at a single contraction (85 X 8 X 3 -f 12 = 170).

The internal structure of muscles bears an important relation to
the force and distance of their contractions, as the principles just
stated indicate. We have noticed how greatly muscles differ in
outward form; they differ quite as much in internal structure,
which is a matter of arrangement of fibers. Two main types of
structure are recognized, the longitudinal and the penniform, but
there are many variations from each type. The longitudinal is the
simpler of the two types; in its simplest form it can be well illustrated
by the pronator quadratus (Fig. 71), a small muscle on the front
of the forearm just above the wrist. This muscle consists of a
single flat sheet of parallel fibers extending across the forearm,
joining the radius on the outside and the ulna on the inside, cover-
ing a space about 2 inches square. This gives us fibers 2 inches
long and therefore able to contract through about 1 inch of distance.

In order to illustrate how muscular structure is related to mus-
cular work, let us assume, for the sake of argument, that this muscle
has 800 fibers, each 4 cms. long and each able to exert a force of
1 gm. (Fig. 4, A). Under this supposition the muscle can exert a
force of 800 gms. through a distance of 2 cms., doing 1600 gm.
cms. of work at one contraction. Now suppose the muscle split
lengthwise and the halves placed end to end, making a muscle of
exactly the same bulk, with half as many fibers twice as long
(Fig. 4, B); it can now pull with a force of 400 gms. through 4
cms. of distance, doing 1600 gm. cms. of work as before. Now
let it be split in the same way again and its length doubled, giving
a muscle of 200 fibers 16 cms. long (Fig. 4, C) ; now it can lift 200
gms. through 8 cms., doing the same amount of work. Evidently

MUSCULAR STRUCTURE AND ACTION

the number of variations in the arrangement can be multiplied
indefinitely, showing that a longitudinal muscle having a certain
bulk will do its work in different ways according to number and
length of its fibers, still doing the same amount of work in every
case.

Origin

. Origin

Mil S

ele

Weight
800 gr.

Origin

400 gr.

200 gr.

Fig. 4. — Diagram of three longitudinal muscles, showing how number and length
of fibers affect power and extent of movement. A has 800 fibers 4 cms. long, B has
400 fibers 8 cms. long, and C has 200 fibers 16 cms. long. Arrows indicate extent of
contraction.

As a matter of fact the many longitudinal muscles in the body
illustrate just so many different arrangements on the same general
plan, alike in consisting of parallel fibers running lengthwise of the
muscle and differing in bulk and in the number and length of
fibers. As two extreme instances we may take the sartorius (Fig. 92),
which is a narrow band of extremely long fibers, suited to perform

MUSCULAR STRUCTURE AND ACTION

Origin

■Tendon

luscle

a movement with little force through an enormous distance, and
one of the intercostals (Fig. 136), consisting of a great number of
very short fibers joining two adjacent ribs and able to draw them

nearer through a slight distance with a
great force.

It is evident from the above that any
muscle arranged on the longitudinal plan
must be short and broad to have much
strength of contraction; if it is long and
slender it is sure to be weak, although it
can shorten through a proportionately
great extent. Fully three-fourths of all
the muscles are situated where they need
to exert more strength than a longitu-
dinal muscle would have, while the greater
extent of contraction would be wasted,
and as a consequence the longitudinal
plan is replaced by the penniform.

The simplest penniform arrangement
is illustrated by the peroneus longus (Fig.
113). This muscle, almost as long and
slender as the sartorius, must be able to
lift the whole weight of the body and
therefore must consist of a great many
short fibers instead of a few long ones.
To secure this structure a long tendon
extends far up the outside of the leg
parallel to the bone and the muscular
fibers arise from the bone and join the
tendon after extending diagonally down-
ward and sideward for an inch or there-
about. The biceps (Fig. 50) presents a
similar case. It is nearly a foot long but
the movement it needs to make is not
far from 3 inches; at the same time it
must have great force. A longitudinal
muscle would be able to shorten more
than is useful here while it would lack
force. To get the exact proportion of
force and distance called for by the work
to be done two tendons extend downward,
from the shoulder and one tendon from below extends upward
between these two; fibers just long enough to give the needed extent
of movement pass diagonally across from the upper to the lower
tendon, giving a bipenniform muscle. Many examples of this plan

Muscle-

-Tendon

Fig. 5. — Diagram to show
how a penniform arrangement
of its fibers can give a long,
slender muscle, like C in Fig.
4, the same lifting power as a
short, thick muscle like A.

MUSCULAR STRUCTURE AND ACTION

of structure will be noticed as we proceed with the study of individual
muscles. Probably the most notable example is the gastrocnemius
(Fig. 113), which contains several penniform sheets and bundles
formed into a well-rounded muscle.

It is easy to get a fair estimate of the strength of longitudinal
muscles, for by cross-sections made in the dissecting room the area
can be readily obtained with a
fair degree of accuracy, and the
parallel direction of all the fibers
makes it easy to get cross-sec-
tions at right angles to the fibers.
When we wish to know the
strength of a penniform muscle
the problem is very different, for
a simple cross-section of such a
muscle is oblique to the direction
of its fibers and may not include
half of them. In complex cases
there is no apparent way to
get the true cross-section. This
method of learning about the
strength of muscle is also lacking
in that it gives us no knowledge
as to the condition of the muscle
and we have to assume it to be
some arbitrary percentage of
what it ought to be to make an
estimate at all. Another way to
determine muscular strength is
by using a dynamometer. There
are two types of dynamometer
used for this purpose: one to test
the muscular system as a whole
and the other to test isolated
groups of muscles. The first
type of dynamometer is illus-
trated by the kind used in col-
leges to test the strength of lift
(Fig. 6) ; the second by the kind used to test strength of grip. The
former is useful to test a man's general strength, and requires but
little time; if we wish to know how a man's strength is distributed
we have to use a form of dynamometer that will test the strength of
each muscle group separately (Fig. 7) . This method does not give
the actual pull of each muscle but its effective pull through its lever-
age as it normally works; this can be compared with the strength
of other men, giving us after all a fair estimate of condition.

Fig. 6. — Use of a dynamometer for
testing the general strength of the
muscular system.

MUSCULAR STRUCTURE AND ACTION

A muscle can exert its greatest force when it is fully extended,
and as it shortens its force diminishes. It follows that if we load
a muscle with all it can lift it will be able to lift it but a short dis-
tance. The question arises, how large a load should be put- upon
a muscle if we wish it to work with best results? This is a problem
frequently tested out in the physiological laboratory, using the

Fig. 7. — Use of a dynamometer for testing the strength of separate muscle
groups. The abdominal group is being tested. (Kellogg.)

muscles of frogs. The following table shows the type of result
uniformly obtained from this test. The muscle is given a constant
stimulus :

Weight.

Height.

Work.

Weight.

Height.

Work

0 . . .

. . . 10

6 . . .

. . . 5

1 . .

. . . 10

7 . ■ ■ . .

. 4

2 . . .

. . . 9

8 . . .

. . 3

3 . . .

. . . 8

9 . . .

. . 2

4 . . .

. . . 7

10.. . .

. . . 1

5 . .. .

. . . 6

11 . . .

. . . 0

MUSCULAR STRUCTURE AND ACTION 27

The column marked weight gives the number of gram weights used
to load the muscle in the successive tests ; the figures for height are the
numbers of centimeters the weight was lifted; the figures for work are
the products of weight and height in gram-centimeters. Notice that
the work accomplished is least with the lightest and heaviest weights,
and is most when the weight is about half of what the muscle can lift.
It means that when we use muscle to get work done it pays to take
moderate weights, avoiding the extremely light and extremely heavy
ones. This has been applied in manual labor, and certain companies
who employ shovelers furnish them with shovels that will hold just
21 pounds, which has been found to be the most favorable weight for
the average man. There is reason to believe that such a load for
a muscle is not only best for efficiency but also best for training,
although it would appear to be wise to use heavier loads for a
small part of the time.

An important condition is illustrated in the last line of the above
table, where the weight is too great for the muscle to lift. If we
apply the formula W = F X D we get 0 for the work. This
means that in the mechanical sense no work is done, although if
we watch the muscle we see that it contracts and exerts force,
which involves destruction of tissue and consequent fatigue. It is
usual to say, in explanation of the apparent contradiction, that in
such a case a muscle does internal work but no external work. We
shall see later that the muscles of the body do a great amount of
useful work without causing motion, as illustrated in standing,
sitting, holding a weight in the hand or on the shoulder, or hanging
by the hands; also in holding a bone solidly in place that it may
serve as a firm support for the pull of another muscle. Such con-
tractions are called static contractions; they result in some muscular
development but are not so good for that purpose as those that
cause motion.

A further extension of the same principle is shown when we use
muscles to oppose a movement but not strongly enough to stop it,
as in lowering a weight slowly, walking down stairs or in wrestling
with a stronger opponent. Such actions of muscle may be called
lengthening contractions to distinguish them from the static and
from the usual shortening contractions. Each kind of action has
its use. We may summarize by saying that muscular work may
involve shortening, static, or lengthening contractions according
as the force of contraction exceeds, equals, or is less than the
resistance.

Football players have known for many years that a man can start
quicker and push harder if he is in a crouching posture, and a few
years ago it was discovered that sprinters can get the quickest
start by assuming a similar attitude. This is for the same reason

28 MUSCULAR STRUCTURE AND ACTION

that men stoop low when they have to lift heavy loads and racing
bicyclists stoop low over their handle bars in making their best
efforts. Since every muscle can pull with most force when it is
fully elongated, all those who are trying to exert all the force at
their command naturally take a position that will put the muscles
that are to be used on a stretch. Everyone will think of instances
of this kind in sport and industry. L_j

Fig. 8. — How a rubber band aids in studying the action of a muscle.

METHODS OF STUDYING MUSCULAR ACTION.

There'are at least five ways of studying a muscle to find out its
action.

1 . Study of the conditions under which a muscle acts by the use
of a mounted skeleton, noticing its points of attachment, direction
of pull, leverage, and any other points bearing upon the problem
that can be discovered. This is a method of study that is of the
greatest value to every student of kinesiology; it is practically
impossible to get a clear idea of muscular action without it. By
the use of cords and rubber bands to indicate the direction of pull,
the study can be made objective and thus aid the memory as well
as the reason (Fig. 8).

METHODS OF STUDYING MUSCULAR ACTION 29

2. By pulling upon the partly dissected muscles of a cadaver
and noticing the resulting movements. This method, has its advan-
tages and was used by the ancient anatomists in studying the ques-
tion, but for the average student it can hardly take the place of
the preceding method. When apparatus for support of the body
can be arranged, as in case of Mollier's experiments, the method
gives excellent results.

3. Stimulation of individual muscles by electric current and
noticing the resulting movements. This method, thoroughly tried
in the classic researches of Duchenne, has corrected many conclu-
sions obtained by the two preceding methods, especially in cases
where the direction of pull and leverage of a muscle make it very
hard to tell which of two things it will do. It is not difficult to
apply this method to superficial muscles, but those lying deeper
could only be reached by it in cases such as Duchenne was able to
find, where the overlying muscles had been destroyed by disease,
leaving the deeper ones intact.

4. The study of subjects who have lost the use of certain muscles
to find what loss of power and movement has resulted and whether
any abnormal postures have been produced. Studies of this kind
are very interesting and some of them have added materially to
our knowledge of muscular action, as we shall see later. It would
be difficult, however, to find such a variety of defective subjects
as is necessary to study the muscles in a systematic way by this
method.

5. Study of the normal living body to find out what muscles
contract in certain exercises and what movements call certain
muscles into action. This, with the first, are the most practical
methods of study, not only for the beginning student, but also for
those who are engaged in the solution of unsettled problems.
Normal subjects are always at hand and are plentiful in the swim-
ming pools and dressing rooms of college gymnasia. Whatever
we may learn from other methods, this one must give the final
decision, for neither observation of a skeleton or electric stimulation
can tell what a muscle will do, although these methods may tell
with certainty what it can do. We need, to learn not only what
action a muscle is able by its position and leverage to perform, but
also what, in an actual case of exercise, the nervous system calls
upon it to do and when it permits it to lie idle. Some of Duchenne's
most brilliant discoveries by means of electric stimulation have
been shown to be misleading, because observation of the living
body shows that certain muscles which might help greatly in an
exercise actually never do so.

The interest of the student of kinesiology is stimulated by con-
stantly recurring practical problems of muscular action to which

MUSCULAR STRUCTURE AND ACTION

he must bring the best evidence secured by all these methods, and
try to verify the commonly accepted solutions by his own observa-
tion of the skeletal mechanism and the action of the living body.
The student who is hopelessly addicted to the study of books as
his only source of information is sure to fall by the wayside.

Articular cartilage
Synovial membrane
Capsular ligament

Fig. 9

Synovial membrane

Articular cartilage

Intra-articular
fibrocartilage

Capsular ligament

Fig. 10
Figs. 9 and 10. — A typical joint.

(Gray.)

Before one can clearly understand descriptions of muscles and
the location of their attachments it is necessary to become familiar
with certain terms used in describing bones and joints. The upper
end of a long bone is usually called its head; the cylindrical portion
forming most of its length is called its shaft. A long and rather
slender bony projection is called a spine; a shorter projection is
called a process, and if pointed a spinous process; a rounded promi-
nence is called a tuberosity, and if small a tubercle. A depression in a
bone is called a fossa, and a hole into or through a bone is called
a foramen.

METHODS OF STUDYING MUSCULAR ACTION 31

The junction of two bones is called an articulation, of which
there are several kinds. The bones of the skull and those of the
pelvis are so joined as to permit no movement; articulations that
permit movement are commonly called joints. The vertebrae of
the spinal column are joined with a disk of cartilage between, the
movement being due to the yielding of the disks; the name amphi-
arthrosis is applied to these joints. Many joints, like those of the
wrist and foot, permit only a slight gliding of one bone upon another;
these are called arthrodial joints. Others permit wide movement
in one plane, like the elbow and ankle, and are called hinge joints.
A few, like the wrist-joint, permit movement freely in two planes,
but no rotation; such are called condyloid joints; finally we have
the ball-and-socket joints, like the shoulder and hip, permitting free
movement hi all planes and rotation on an axis besides.

Articulating surfaces of bone are always lined by a synovial
membrane, which is reflected across from one bone to the other to
form a closed sac. The synovial membrane secretes a fluid, called
the synovial fluid, which lubricates the joint and so prevents any
considerable friction. In most joints there is at least one piece of
cartilage to form a surface of contact, movement apparently taking
place with less friction between bone and cartilage than between
two bones. The bones forming a joint are kept in place by strong
bands of connective tissue called ligaments. They are usually less
elastic than tendons, and connect bone to bone as shown in Figs.
9 and 10. The several ligaments surround the joint and their
edges are always joined to form a closed sac called a capsule which
serves to protect the joint and to prevent rupture of the synovial
membrane and escape of the fluid.

CHAPTER II.

THE BONES AS LEVERS.

A lever is a rigid bar revolving about a fixed point, which is
called its axis or fulcrum. In the making of bodily movements it
is the principal function of the bones to serve as levers, and the prin-
cipal function of the muscles to move these levers. It is only by
such action that the body is able to stand erect, moves itself in the
various forms of locomotion, and move objects outside of itself.
The student of kinesiology must therefore be thoroughly familiar
with the fundamental principles of leverage in order to get even an
elementary conception of the bodily mechanism.

iva, 1

pa, 2

pa, 3

III

wa, 1

>
pa, 1

wa, 3

Fig. 11. — The three classes of levers. The long straight lines are the levers,
A is the axis, the squares represent the weight or resistance and the arrows the
power or pull of muscle; pa, power arm; wa, weight arm.

A rigid bar, such as one of the bones of the arm, may have vari-
ous degrees of usefulness for a certain purpose, depending on the
location of three points upon it : the point where the force is applied .
to it, the point where it is applied to the resistance we wish to over-
come, and the axis on which it turns. Levers are divided into three
classes according to the relative position of these three points, as
illustrated in Fig. 11.

Levers of the first class have the axis between the other two

THE BONES AS LEVERS

points, and as a consequence the force and the resistance act in the
same direction and the two arms of the lever move in opposite
directions. This class of levers is illustrated by a crow-bar, a pump-
handle, the walking-beam of a side-wheel steamer, a pair of scissors,
or by muscle I in Fig. 12.

Levers of the second class have the resistance applied between
the force and the axis; the force and the resistance act in opposite
directions and the force required is always less than the resistance.
This class is illustrated by the action of a wheelbarrow or a pair of
nut-crackers. There are few if
any levers of the second class in
the body.

Levers of the third class have
the force applied between the
resistance and the axis; force and
resistance work in opposite direc-
tions and the force must always
be greater than the resistance.
The action of a spring for closing
a door is an example of third-
class lever, also the pedal of a
bicycle and the muscle marked
III in Fig. 12.

The distance from the axis to
where the force is applied to the
lever may be called the force-
arm, power-arm, or muscle-arm
of the lever, while the distance
from the axis to the place where
the resistance is applied may
be called the resistance-arm or
weight-arm. In Fig. 12 AL is
the power arm and AB the
weight arm for muscle III. The
law of levers, which applies to
levers of all classes alike, states

that the force will exactly balance the resistance when the prod-
uct of the force by its arm is equal to the product of the resist-
ance by its arm ; in other words, when the force and resistance are
inversely proportional to their distances from the axis. Notice how
the figures for weights and distances in Fig. 11 illustrate this. If the
muscle-arm in case of muscle III in Fig. 12 is 2 inches and the weight-
arm is 12 inches, a force of contraction of 48 pounds will hold a
weight of 8 pounds in the hand (2 X 48 4- 12 = 8). Any reader
who is not familiar with the use of levers should study the effect of
3

Fig. 12. — Illustration of first class
and third class levers by muscles act-
ing on the elbow-joint. The bone AR
is the lever, with the axis at A, the
weight or resistance at the hand, which
is beyond R, M, M are the muscles and
L is the insertion of the muscle III.

34 THE BONES AS LEVERS

changing the length of the muscle-arm and the weight-arm on the
force of muscle that will have to be used to lift the weight by making
and solving problems similar to the above.

When a lever turns about its axis it is evident that all points
upon it move in arcs of a circle and that the distances these points
move is proportional to their distances from the axis. In the case
of muscle III, for example, if the weight is six times as far from
the axis as the muscle, it will move six times as far, so that
when the muscle contracts through 1 inch the weight will be lifted
through 6 inches. The relation of this fact to the law of levers
given above is stated in the law of conservation of energy, which
says that in the use of levers all that is lost in force is gained in
distance, and vice versa. Since the time it takes a muscle to shorten
is not affected by the length of the lever-arms, it follows that any
gain in distance is a gain in speed as well.

In the common form of levers seen in familiar tools and machines,
such as pumps, scissors, nut-crackers, and the like, the resistance
is applied close to the axis and the force much farther away, since
the lever is used to gain force at the expense of distance of move-
ment. In the body, as illustrated by the two muscles in Fig. 12,
the force is usually applied with a short muscle-arm to overcome a
resistance much farther away; the penniform arrangement of muscle
fibers gives a large amount of force and the leverage is such as to
give great distance of movement and speed. This plan of construc-
tion not only gives the body all the power, speed, and extent of
movement that is needed but also compactness of structure, the
muscles lying much closer to the bones than would be possible with
longer muscle-arms.

Besides the effect of relative length of lever-arms, the action of
muscles is varied by the direction in which they pull upon the lever.
In solving elementary problems of leverage it is usual to assume,
as we have done in the examples above, that the force is applied
at right angles to the lever, but in the action of muscles on the
levers of the body this is the exception rather than the rule. Fig.
12 shows two muscles pulling at nearly a right angle, but it is plain
that if the joint were in any other position they would not do so,
and in the positions of extreme flexion and extension of this joint
they will pull at a much smaller angle. Many muscles, as we
will notice as we proceed, never pull an angle greater than 20
degrees.

Fig. 13 shows how the angle of pull changes as a muscle shortens.
When the bony lever is in the position BC the angle of pull, DEB,
is 12 degrees; in the position BC, it is 20 degrees, at BC, 25
degrees, etc. The angle of pull will never be as great as a right angle
unlessthe origin D is farther from the axis than the insertion, E.

THE BONES AS LEVERS 35

The smaller the angle of pull, the farther and faster will a certain
amount of contraction move the bone, as may be seen by Fig. 13.
The muscle DE is represented in this diagram as contracting four
times, each time by the same amount (one-eighth of its full length) .
Starting from the position BE, where the angle of pull is only 12
degrees, the first shortening turns the bone BE through an angular
distance of 32 degrees, but as the angle of pull increases the same
amount of shortening only turns it 25, 21 and 19 degrees. Pulling
at an angle of 10 to 12 degrees the point E moves more than three
times as far as the muscle shortens; when the pull is at a right angle
the contraction and the resulting movement are practically the same.

Fig. 13. — Diagram to show how angle of pull changes as the bony lever is moved
by the muscle: AB is a stationary bone with axis at B; DE is the muscle and BC
the moving bone, coming to positions BCi. BCi, etc., as the muscle shortens, the
muscle coming to positions DEi, DEi, etc., DEB is the angle of pull.

The gain in speed and distance that a muscle secures when it
pulls at a small angle is balanced by a loss of power that is illustrated
in the diagram of Fig. 14, known as the "parallelogram of forces."
As in the preceding Fig., AB is a stationary bone and BC a moving
bone with the axis at B; BE is the muscle, pulling at the angle
DEB. The muscle pulls on its insertion at E in the direction of
D, but the rigid bone BE will not permit E to move that way, but
rather resolves the pull of the muscle into two forces — one of which
acts in the direction EG to move the bone on its axis and the other
in the direction EB to move the bone lengthwise and only serves
to increase the friction in the joint at B. Now it is found experi-

THE BONES AS LEVERS

mentally that if we choose any point on DE, as F, and construct
the rectangle HEGF, with the two lines perpendicular to BC
and the third line parallel to it, the length of the side EG will
represent accurately the useful part of the muscle's force and HE
the ineffective part, while the diagonal FE represents the entire
force of pull. It is clearly seen by a look at the diagram that as
the angle of pull, DEB, changes the length of the sides of the
rectangle will change; with the larger angle of pull that exists when
the point E is moved to E' it takes the form H'E'G'F', with the
relative length of sides reversed.

Fig. 14. — The parallelograms of forces: AB, stationary bone; BC, moving bone;
B, axis; DE, muscle; BC, another position of BC, DE taking the position DE'.
DEB and DE'B, angles of pull; FGEH and F'G'E'H', the parallelograms of forces.
See text.

The relation of the side EG to the diagonal EF is constant for
each size of the angle DEB, and the ratios for the different sizes
of the angle have been computed and can be found in the table on
p. 39. This ratio is called the sine of the angle, and the useful
component for any angle can be found by multiplying the entire
force of the muscle by the sine of the angle at which it pulls. The
mathematical formula is / = F X s, in which / is the effective
force, F is the entire force, and s is the sine of the angle of pull.

To illustrate how this formula is applied to problems of muscu-
lar action, let us assume that the muscle DE, which is pulling on
the lever at an angle of approximately 27 degrees, is contracting
with a force of 100 pounds. In the table of sines we find the sine

THE BONES AS LEVERS

of 27 degrees to be 0.45399; placing these values in the formula it
becomes / = 100 X 0.45399, which gives 45.399 pounds as the
effective force. To find the force acting lengthwise of the lever
we find the angle HFE (90 — 27 = 63) and proceed as before.
/ = 100 X 0.89101, or 89.101 pounds. In this case, therefore, the
diagonal represents 100 pounds and the two sides 45.3 and 89.1
pounds.

While we are considering angle of pull it is well to notice that
the resistance as well as the muscle may act at various angles.

When the resistance is a weight it will always act vertically down-
ward. In Fig. 15 the weight is shown pulling down on the bony lever
at an angle of 45 degrees; when the lever is in a horizontal position
this pull is at 90 degrees, but in other positions it acts at smaller
and smaller angles, so that its force, like that of the muscle, is
resolved into an effective component acting at right angles to the
the lever and an ineffective component acting lengthwise of it.

■4s<

10 j

Fig. 15. — Conditions of action of a muscle acting on the elbow-joint to lift a weight
in the hand: S, shoulder; E, elbow, M, muscle; H, hand; L, lever.

To illustrate fully how the muscular requirement is influenced
by these elements of leverage and how to attack such problems,
let us inquire with what force a muscle acting on the elbow-joint
must pull to lift 10 pounds in the hand when the forearm is 45
degrees above the horizontal, the muscle-arm being 2 inches, the
weight-arm 12 inches, and the angle of pull of the muscle 75 degrees.

The conditions of this problem are illustrated by Fig. 15. Evi-
dently the weight will act upon the lever so as to resist the action of
the muscle with a force equal to 10 pounds multiplied by the sine
of 45 degrees, or 7.07 pounds. This multiplied by its lever-arm
(7.07 X 12) gives 84.84 inch-pounds to be overcome by the action
of the muscle. From the law of levers we have / X 2 = 84.84, or

THE BONES AS LEVERS

f = 42.42 pounds. This is the effective force that must be produced
by the action of the muscle at an angle of 75 degrees (sine = 0.96593).
We wish to find F, so in the formula / = F X s we substitute the

known quantities, giving the formula,
42.43 = F X 0.96593, or F = 42.42 +
0.96593, from which F or the whole force
of contraction is 43.9 pounds.

In applying the general principles of
leverage to bones it is necessary to bear
in mind that the two arms of a lever are
two straight lines drawn from the two
other points to the axis; in some cases
these two may form one and the same
straight line, but usually not. In case of
the humerus, for example, the point of
contact with the scapula that serves as
the axis of the shoulder- joint is an inch
or more to one side of the shaft of the
bone; as a result the two lever arms meet
at a rather large angle, as shown in Fig.
16. In most cases we have one principal
resistance, and therefore one resistance-
arm, with several muscles acting, each
with its own muscle-arm, making a com-
plex lever with several forces acting on it
at once. The angle at the axis has no
effect on the law of leverage, for as long
as the lever is a rigid bar it acts in the
same way whether it is straight or not.
To solve cases of combined muscle action
we may work each one out separately as
if it acted on the resistance by itself, and
then add the results, or we may multiply
each force by its arm and add the prod-
ucts before applying the law of levers.
To illustrate: suppose that two muscles
pull on the humerus at Sp and D (Fig.
16) with a force of 100 pounds each, the
muscle-arm at Sp being 1 inch and the
angle of pull 60 degrees, the muscle-arm
at D 5 inches and the angle 15 degrees;
how much resistance will they overcome
at a distance of 12 inches down the arm? The product for Sp will be
1 X 100 X 0.86603, or 86.603; the product for D will be 5 X 100 X
0.25882, or 129.41; the sum of the two is 216.013; by the law of

Fig. 16. — The humerus, to
show the lever arms upon it:
A, axis; Sp, lever-arm of
supraspinatus ; Sc, of supra-
scapularis; Pm, of pectoralis
major; D, of deltoid; C, of
coracobrachialis.

THE BONES AS LEVERS

levers r = 18.001 pounds. This is the effective resistance; if the
resistance acts at an angle less than 90 degrees, the total resistance
overcome will be the number just given divided by the sine of the
angle at which it acts.

Very often the resistance to muscular action is the weight of a
part of the body, and when this is the case we must not only know
the weight of the part but also its distance from the axis. In all
cases of this kind the weight is assumed to be at the center of
gravity of the part and the weight-arm of the lever measured from
that point. These points have been worked out carefully. For
example, the center of gravity of the whole arm is slightly below
the elbow; for the lower limb just above the knee, etc.

TABLE OF SINES.

Degrees.

Sines.

Degrees.

Sines.

Degrees.

Sines.

Degrees.

Sines.

0 or 180

.00000

23 or

157

.39073

46 or

134

.71934

69 or

111

.93858

1 or 179

.01745

24 or

156

.40674

47 or

133

.73135

70 or

110

.93969

2 or 178

.03490

25 or

155

.42262

48 or

132

.74314

71 or

109

.94552

3 or 177

.05234

26 or

154

.43837

49 or

131

.75471

72 or

108

.95106

4 or 176

. 0697.6

27 or

153

.45399

50 or

130

.76604

73 or

107

.95630

5 or 175

.08716

28 or

152

.46947

51 or

129

.77715

74 or

106

.96126

6 or 174

.10453

29 or

151

.48481

52 or

128

.78801

75 or

105

.96593

7 or 173

.12187

30 or

150

. 50000

53 or

127

.79864

76 or

104

.97030

8 or 172

.13917

31 or

149

.51504

54 or

126

.80902

77 or

103

.97437

9 or 171

.15643

32 or

148

.52992

55 or

125

.81915

78 or

102

.97815

10 or 170

.17365

33 or

147

.54464

56 or

124

.82904

79 or

101

.98163

11 or 169

.19081

34 or

146

.55919

57 or

123

.83867

80 or

100

.98481

12 or 168

.20791

35 or

145

.57358

58 or

122

.84805

81 or

.98769

13 or 167

.22495

36 or

144

.58779

59 or

121

.85717

82 or

.99027

14 or 166

.24192

37 or

143

.60182

60 or

120

.86603

83 or

.99255

15 to 165

.25882

38 or

142

.61566

61 or

119

.87462

84 or

.99452

16 or 164

.27564

39 or

141

.62932

62 or

118

.88295

85 or

.99619

17 or 163

.29237

40 or

140

.64279

63 or

117

.89101

86 or

.99756

18 or 162

.30902

41 or

139

.65606

64 or

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65 or

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88 or

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20 or 160

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43 or

137

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66 or

114

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21 or 159

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136

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67 or

113

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1.00000

22 or 158

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45 or

135

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68 or

112

.92718

CHA[PTER III.
MUSCULAR CONTROL.

Civilized man is inclined to show a certain amount of scorn for
what he is in the habit of calling "mere muscle," but the fact
remains that everything he does depends ultimately on the action
of muscles. The muscle fiber is, in the last analysis, the sole instru-
ment by which the human will can act upon the outside world.
No matter how great the refinements of civilization, no matter
how much machinery may be devised to do our work for us, man
can never get away from the necessity for muscular work. The
people of the "intellectual classes" do not escape muscular work;
they only use small muscles instead of large ones.

Each muscle fiber is an independent unit, isolated from all its
near neighbors by its sarcolemma as completely as if it were miles
away. Normally a muscle fiber receives no communication during
its whole life except from the nervous system. Although it can be
made to act by an electric shock or a violent blow, these are rude
departures from normal conditions. The muscle fiber is made to
do just one thing : contract, and it is made to do this only when it
receives the signal to do so through its nerve fiber. The nervous
mechanism by which the million or more of muscle fibers in the
body are controlled so as to perform powerful and graceful move-
ments is one of the most interesting subjects of study. Surely no
one can have greater interest in it than the student of kinesiology.

NEURONES.

The structural unit of the nervous system is the neurone. It con-
sists of a nerve cell with all of its branches. The cell is a minute
mass of protoplasm containing a nucleus; the branches are called
nerve fibers. Neurones are so radically different in form from any-
thing else in nature that for a long time they baffled comprehen-
sion. The feature that caused the trouble is the enormous length
of the fibers in comparison with the size of the cell to which they
belong. The cells are less than one-tenth of a millimeter in diam-
eter, while the fibers are sometimes a meter long. Fig. 17 shows a
neurone correctly in all details except this one; if the artist had
drawn the main fiber of proportionate length to the size of the cell

NEURONES

it would be rpore than 500 feet long; we need to bear in mind, there-
fore, that while the figure shows diameters magnified 25 to 30
times, the length of fibers is reduced to T^¥ or yto~o °% the pro-
portional extent.

NERVE CELL.

^DENDRITES.

AXIS-CYLINDER PROCESS.

-COLLATERAL BRANCH.

"MEDULLARY SHEATH.

AXIS-CYLINDER
CLOTHED WITH
MEDULLARY "
SHEATH.

-AXIS-CYLINDER.

MEDULLARY- — /
SHEATH AND \

NEURILEMMA. \

-NEURILEMMA,

AXIS-CYLINDER

CLOTHED WITH ■

NEURILEMMA.

/TERMINAL BRANCHES.

Fig. 17. — A neurone. (Stohr.)

The principle of division of labor is illustrated in the activities
of a single neurone. The cell with its nucleus serves as a reservoir
of food material and presides over the nutrition and growth of the
entire neurone, even to the ends of its longest fibers. A fiber cut
off from its cell dies, but the cell may send out another to replace
it. The fibers carry messages. That which travels along the fiber

42 MUSCULAR CONTROL

is called a nerve impulse, and may be thought of as a wave of
energy or excitement. Impulses travel on the nerve fibers of man
at the rate of about 100 feet per second. The central thread of
nerve substance in a fiber, on which the impulse travels, is called
the axis-cylinder; it is protected through most of its length by a
delicate membrane called the neurilemma, similar to the sarco-
lemma of a muscle fiber. Within the neurilemma is usually a
white fatty sheath called a medullary sheath. The sheaths insulate
the central thread and prevent the impulses from spreading to
other fibers.

The endings of some fibers are developed into special organs for
receiving messages; the endings of others into organs for trans-
mitting messages to muscle, gland, or other neurones. This gives
rise to a division of nerve fibers into axones and dendrites. The
axone is the principal branch of a neurone and is the path by which
impulses pass from the cell; most forms of the neurone have but
one axone. Most neurones have several dendrites, which are the
paths of impulses going to the cell.

The further study of neurones as a factor in muscular control
requires an explanation of how they are distributed in the body,
and this calls for a brief survey of the nervous system as a whole.

THE NERVOUS SYSTEM.

It is usual to distinguish two main divisions of the nervous
system — the central portion, lying within the neural canal in the
spinal column, and the peripheral portion, which includes the
cranial and spinal nerves. The central portion includes the brain
and the spinal cord. The nerves are bundles of nerve fibers that
branch off from the central nervous system in 43 pairs. Another
part, called the sympathetic nervous system, is not concerned in
voluntary movement and hence will be omitted in our study.

The brain, lying within the skull, includes the cerebrum, the
cerebellum, and several large groups of nerve cells called the " basal
ganglia." The medulla oblongata connects the brain and the spinal
cord. The central nervous system is separable into a gray and a
white portion; the gray portion is on the outside in the cerebrum
and cerebellum, forming a thin layer called the cortex. The area
of the cortex is greatly enlarged by deep folds called convolutions.
Within the cortex is the white portion of the brain, with the basal
ganglia scattered through it.

The spinal cord is a cylindrical column about 18 inches long and
about half an inch in diameter at an average; its diameter differs
considerably in different places, two enlargements at the levels of
the arm and leg being of most importance. The spinal cord consists

THE NERVOUS SYSTEM

of a vast number of neurones, along with the supporting tissues,
called neuroglia, and the blood and lymph vessels. It is deeply
cleft lengthwise by two fissures, the anterior and posterior median
fissures, dividing it into its right and left halves. The fissures
serve as a convenient guide to the study of the cord, since the
anterior fissure is always an open one while the posterior fissure is
always closed (Fig. 26), making it easy to distinguish directions.
Cross-sections of the cord show the gray and white portions dis-
tinctly, the gray portion being within and entirely enclosed by the

white portion. The gray portion
is shaped much like a capital
H; the four extremities of the
H, as seen in Fig. 19, are cross-
sections of four columns or ridges
that extend up and down the

Fig. 18. — The central portion of the
nervous system. (Gerrish.)

Fig. 19. — General structure of spinal
cord and junction of a spinal nerve with
it. (Gerrish.)

whole length of the cord. The cross-bar of the H is called the
commissure, and is the place where nerve fibers cross from one side
of the cord to the other.

The spinal nerves leave the cord in pairs, one pair for each verte-
bra; one is on the right and its mate on the left side. Each nerve
joins the cord by two roots; one opposite the tip of the anterior
gray column is called the anterior root, and one opposite the pos-
terior gray column is called the posterior root. The two^ roots join
to form a nerve before they pass out of the neural canal; just before

MUSCULAR CONTROL

they join the posterior root has an enlargement upon it that is
called a spinal ganglion (Fig. 19).

The four roots and the two fissures divide the outer or white
part of the cord into six columns that extend its whole length:

two anterior, two lateral, and two
posterior. Microscopic study of the
structure of these white columns shows
it to be composed of medullated nerve
fibers, each of which has the structure
of the main fiber shown in Fig. 17.
The medullary sheath is what gives
this part of the cord its white appear-
ance, leading the early anatomists to
believe that there are two kinds of
nerve substance, white and gray.
Looking at a cross-section of the cord
in a microscope we see cross-sections
of these nerve fibers, each one appearing as a circle with a dot in the
center (Fig. 20). The circle is the neurilemma and the dot is the
axis-cylinder. The greater portion of fibers seen in any section pass
in a vertical direction; a smaller number are usually seen passing
across horizontally.

Fig. 20. — Cross-section of a
white column of the spinal cord.
(Klein.)

Fig. 21.

-Cross-section of spinal cord on the border of gray and white portions.
(Klein.)

Microscopic study of the gray part of the cord shows it to consist
mainly of nerve cells and naked nerve fiber$. The fibers form here
a confusing jungle or network, having no uniformity of direction;

MOTOR NEURONES 45

nerve cells of various sizes and shapes are seen scattered through
it. Some of the fibers seen are the dendrites of the nerve cells that
lie among them; some are the axones of these cells; some are the
terminals of axones from nerve cells situated far away in distant
parts of the nervous system. It is here, where cells and fibers
have no insulating sheaths, that neurones are able to influence one
another (Fig. 26).

The above description of the nervous system, dealing with its
general form and appearance, is of value only as it leads to a knowl-
edge of its internal structure and activities. From the latter view-
point the nervous system, so far as it concerns us here, consists of
three systems of neurones: the motor, sensory, and association
systems. The motor neurones constitute the only path by which
impulses can be sent to the muscle fibers; the sensory neurones pro-
vide the only path by which stimuli can enter the nervous system
from the outside world; the association neurones are the means of
communication between the various parts of the nervous system
and hence are the only possible means of muscular coordination.

MOTOR NEURONES.

The cells of the motor neurones are situated in the anterior gray
columns of the spinal cord, forming two long groups of cells extend-
ing the whole length of the cord. From each of the cells, which are
like that shown in Fig. 17, arise several dendrites that may extend
for varying distances through the gray part of the cord but never
outside of it; they pass up, down, toward the posterior column,
or through the commissure to the opposite half of the cord. It is
through these dendrites that the motor neurones receive their
stimuli.

Each motor neurone has a single axone (Fig. 17). From the cell
in the anterior gray column the axone passes outward across the
white part of the cord, traverses the anterior root of a spinal nerve
and then follows the course of the nerve and one of its branches to
a muscle.

Since each muscle fiber is so completely insulated from its fellows,
each must have its own nerve fiber, and each nerve fiber must be
so insulated that no message can jump across from one fiber to
another in the nerve, where they lie side by side for long distances.
The neurilemma and the medullary sheath serve this purpose.
Many of the motor axones have several terminal branches, one
neurone controlling several muscle fibers; evidently these must be
fibers that will always need to act together. Four hundred thousand
motor axones have been counted in the anterior nerve roots of a
single individual. These axones enter the muscle along with sen-

MUSCULAR CONTROL

sory fibers, forming a mixed nerve; the nerve divides in the muscle
and the fibers go to the various parts; each motor fiber finally
terminates inside of a muscle fiber with an ending like that shown
in Fig. 22. The office of this ending is to transmit to the proto-
plasm of the muscle fiber the message sent by the cell in the spinal
cord. Under normal conditions it never conveys messages in the
other direction.

- it
/. - -

■ - X *> " n •--

; ■■■-■■ T

" , « *

Fig. 22. — Motor nerve ending in a muscle fiber. (Klein.)

If one of the limbs of an animal is severed from its body the
muscles in such limb may still be made to contract by stimulat-
ing the nerve. The motor fibers in the nerve, when stimulated,
convey the message to the muscle fibers and they contract, just as
if the message came from the animal's nervous system; with this
difference: muscular actions arising in this way are not regulated
and controlled so as to be useful. The machinery for muscular
control lies within the brain and spinal cord.

SENSORY NEURONES.

The neurones of the sensory system have their cells situated in the
so-called "spinal ganglia" on the posterior roots of the spinal nerves
(see Figs. 19 and 24). These neurones are of a form utterly unlike
the motor neurones. The cells are roughly spherical, without den-
drites, and with one axone that shortly divides into two. One of

SENSORY NEURONES

these branches serves as a dendrite; it passes outward along the
posterior root to the nerve and then along the nerve to terminate in
the skin, muscle, bone, or other tissue, where it has an ending
specially adapted to receive stimuli. There are in each individual
somewhere from half a million to a million of these sensory neurones,
each with an axone extending out to some part of the body. They
are to be found everywhere but are most numerous in the skin.
Endings near the surface give rise to sensations of taste, touch,

• tV- *S8

Fig. 23. — Sensory nerve ending in muscle. (Klein.)

temperature, etc., while others in muscles and tendons make us
aware of the force of muscular contractions and the positions of the
body (Figs. 2 and 23).

The second branch of each sensory axone extends from the cell
in the spinal ganglion along the posterior root into the spinal cord,
where it penetrates the posterior white column for a short dis-
tance and then divides into an ascending and a descending branch.
These two branches extend vertically in the posterior white
column, giving off at intervals horizontal branches called collaterals

MUSCULAR CONTROL

which penetrate the gray portions of the cord and terminate among
the cells and dendrites there (Fig. 24). The ends of these sensory
fibers are often brush-like, and they often intertwine with similar
brush-like endings of the dendrites of the motor neurones, thus
forming what is called a synapse, or point of communication between
one neurone and another.

Everyone knows how a light touch upon the hand of a person
who is asleep may cause the hand to be moved without awaking
the sleeper and without his being aware of it. Such movements,
commonly called "reflexes" because the influence of the touch upon
the skin seems to be "reflected" back from the central nervous

Fig. 24. — A sensory neurone and its branches in the cord. (Kolliker.)

system to the region from which it originated, can be explained
only through a knowledge of the nervous mechanism we are just
considering. The contact or pressure upon the skin stimulates one
or more of the delicate sensory nerve endings in it and as a result
a message or "impulse" passes up the corresponding nerve fibers
to the spinal ganglion, thence to the spinal cord, up and down the
vertical branches of the sensory axone, and along the horizontal
branches to the synapses at their ends. The close intertwining of
the sensory brush endings with the similar endings of the motor
dendrites here makes it possible for the message to pass to the
motor neurone, and once started upon the motor path it can only

ASSOCIATION NEURONES 49

pass out to the muscles and give rise to a contraction. Such a
nervous path, including a sensory neurone, a motor neurone, and
the synapse that connects them is called a "reflex arc." Since the
sensory neurone has two vertical branches and several horizontal
branches it is evident that an impulse starting in the skin on a
single sensory fiber may and naturally will spread to several motor
neurones and thence to a considerable number of muscle fibers.

If instead of touching the sleeping person lightly you hit him a
smart blow on the hand, his response is quite different. As every-
one knows, he is apt to jump, gasp or cry out and contract practi-
cally every muscle in his body, all before he is fully awake or aware
of what he is doing. To see how this can take place as a reflex
resulting from a stimulus over so small an area, we need to notice
how far the branches of the sensory axones extend into the central
nervous system. By ingenious methods that we have not room to
describe here, it has been shown that these minute nerve fibers,
the branches of the sensory axones in the spinal cord, extend up
and down the posterior white columns of the cord for various dis-
tances. Some of them, and in fact the most of them, extend no
farther up or down than the width of one or two vertebrae. This
makes the sensory neurones have most intimate connection with
the motor neurones of the same district. Some of the vertical
branches, comparatively few in number, pass up to the medulla
and. down to the lower extremity of the cord; others are of inter-
mediate length. These make less numerous contacts, by their
synapses, with motor neurones controlling the muscle groups of
distant parts, making it possible for the sleeping person's foot or
his breathing muscles to respond directly to a stimulus given to
the skin of the hand. It is an interesting point that no sensory
fibers cross the cord from right to left nor from left to right, but, as
we have noticed, some of the dendrites of the motor neurones cross
the median line, enabling muscles of both sides to receive a stimulus
given on only one side.

ASSOCIATION NEURONES

Association neurones lie wholly within the central nervous sys-
tem. Their cells are seen in the gray matter of all levels of the spinal
cord and brain. They are by far the most numerous class of neu-
rones in man, including a very large percentage of those in the
spinal cord and practically all those in the brain. The superiority
of man over other animals is due to the more extensive develop-
ment of this class of neurones. They are best studied in separate
groups, of which there are many, each with its peculiarities of
form, location, and function.
4

MUSCULAR CONTROL

We have just seen, in the preceding paragraphs and in Fig. 24,
how the sensory axones branch in the spinal cord with the apparent
purpose of spreading the effect of each sensory stimulus to a wide
range of muscles. It is evident, however, that Nature does not
consider the mechanism of the sensory branching sufficient for the
purpose, for she has provided a group of association neurones to
aid in the same way, making still more intimate connection pos-
sible between sensory and motor neurones and spreading the incom-

Fig. 25.

-An association neurone of the spinal cord: S, sensory neurone; A, associa-
tion neurone; M, M, M, motor neurones.

ing messages still wider. These cells are smaller than either the
sensory or motor cells; they are located in the gray part of the cord
about midway between the anterior and posterior gray columns;
their axones pass out horizontally into the lateral white columns,
where they divide into ascending and descending vertical branches
like the sensory axones. These, like the sensory fibers, have hori-
zontal branches that penetrate the gray part of the cord at all
levels, with synapses connecting them with motor and other cells.

ASSOCIATION NEURONES 51

About half of the axones of these cells cross to the opposite side
of the cord, where they divide and end in like manner, making the
most complete and intimate connection between each sensory area
and practically all the muscle groups of the body.

Nothing is more familiar than the fact that we quickly become
aware of any stimulation of sensory nerve endings in the skin,
messages in some way going to the brain to cause our sensations.
We have thus far seen a path reaching only up the spinal cord as
far as the medulla upon which these sensory messages might go.
A second group of association neurones, with cells situated in the
medulla, performs the office of carrying the sensory impulses up
to the seat of consciousness. They receive their stimuli from the
long ascending branches of the sensory axones, with which they
have synapses, and their own axones pass up and carry the messages
to a higher level. It is likely that another similar "relay station"
exists in the midbrain, most of the sensory impulses passing over
three neurones in succession before reaching the cortex of the cere-
brum, where consciousness resides.

These sensory pathways make possible not only a consciousness
of stimuli applied to the skin but also a consciousness of the extent
and force of muscular contractions and the positions of the parts
of our bodies — the complex sensations commonly known as "mus-
cular sense." The mechanism is the same, except that in place of
the sensory endings in the skin we have those more complex and
interesting ones found in muscles and tendons (Figs. 2 and 23).
The reader can easily observe how fully he can with eyes shut tell
the position of arms, legs or trunk or of almost any particular joint
as he takes various poses, either standing, sitting, or lying flat.
Besides making us aware of the position of the body and the
state of contraction or relaxation of muscles, the mechanism just
described performs another and much more important office. When
we walk, for example, what is it that controls the raising and replac-
ing of the feet upon the ground in proper time? How does it
happen that we repeatedly throw the weight on the forward foot
just as it reaches the right place? It is easy to notice that we pay
no attention to these things under ordinary conditions, although
we do so when we first learn to walk and to a certain extent when
the footing is uneven or insecure. The answer is that the sensory
impulses that give rise to consciousness of position when we pay
attention to it act as a guide to the muscular action when we think
of something else. When the foot has been swung forward just
far enough the nerve endings in muscles, tendons and joints send
messages into the central nervous system that stimulate the muscles
needed to perform the next act in the process.

Extended studies of the question lead us to believe that the cere-

MUSCULAR CONTROL

bellum is the portion of the nervous system that serves as organ or
center for the control of complex bodily movements. The cere-
bellum is closely connected by nerve fibers with the semicircular
canals in the skull, which serve as the organ of equilibrium, and
it also receives many nerve fibers from the body.

Nerve impulses from the body to the cerebellum pass mainly by
means of a third group of association neurones whose cells lie in
the spinal cord. Just posterior to the center of the gray matter of
the cord is a column containing many nerve cells. The place is
called " Clarke's column" and the axones of the cells in it form a
bundle passing upward to the cerebellum and known as the "direct
cerebellar tract." These neurones convey the impulses coming in

Fig. 26. — Cross -section of spinal cord to show the various columns of cells and
fibers: 1, column of Goll; 2, column of Burdach; 3, comma bundle; 6, direct cere-
bellar tract; 7, crossed pyramidal tract; 10, direct pyramidal tract. (Sherrington.)

from the muscular sense endings to the cerebellum, where they
guide the activities of that organ in the control of all complete
bodily exercises.

The cortex of the cerebrum contains a vast number of association
cells whose fibers connect different parts of the cortex and also
connect parts of the cortex with the sense organs and with the
muscles. The latter group is of special interest to us here. We
are all aware that we can move any part of the body at will or pre-
vent any part from moving when we choose to do so. This connec-
tion between the will and the muscles is made by means of a group
of association neurones known as the "pyramidal cells:" They
are situated in the cortex of the cerebrum at the top and sides
along a prominent infolding or fissure known as the "fissure of

STIMULATION AND INHIBITION 53

Rolando." Their axones pass down through the brain and medulla,
crossing from side to side as they pass down, and end at various
levels where they make synapses with the dendrites of the motor
cells of the cord. This bundle of axones is known in the cord as the
"crossed pyramidal tract." A smaller bundle of the same group
near the anterior fissure is called the "direct pyramidal tract."
The reader should note that the pyramidal fibers do not go directly
to the muscles but act upon the motor neurones of the cord, which
in turn control the muscles.

STIMULATION AND INHIBITION.

We are accustomed to think of a nerve impulse as a form of
energy that can cause a muscle to contract, but in order to secure
muscular control and useful movement we must have nerve impulses
that can prevent muscles from acting. The former influence is
called stimulation and the latter inhibition. Careful observation
has shown that whenever a group of muscles contracts normally,
other muscles, the antagonists of the former, are made to relax
at the same time; vigorous action of the flexors of the arm, for
example, is usually accompanied by relaxation of the extensors;
and this is not a. passive failure to act, but an actual inhibition with
less tone than is present in the normal resting state. Such a change
is evidently necessary to the most economical use of the muscles,
for if in making a movement one had always to overcome the tone
of the opposing group force would be wasted, and this is true espe-
cially during excitement, which greatly increases muscular tone.
Inhibition is also necessary to the relaxation of rest, for the sensory
nerve endings are constantly receiving thousands of stimuli from
all kinds of sources, and, as we have seen, any one of these stimuli
may spread to all the muscles; if there were no way to prevent
reflex movements caused in this way, all the muscles would be
stimulated to action all the time and useful movement would be an
impossibility.

Something like this happens when one is affected by a very vio-
lent stimulus, as when a bee stings him or a gun goes off unex-
pectedly close to him. He is apt to scream and jump in a spas-
modic way, but the movement is not coordinated and accomplishes
nothing useful. There is plenty of contraction but no inhibition of
contractions that are more harmful than good. A muscular move-
ment that is properly performed is, quite to the contrary, economical,
graceful, and useful for a definite purpose.

Sherrington, the greatest living authority on this topic, describes
an experiment he has performed many times and which illustrates
both the importance of inhibition in normal muscular action and

54 MUSCULAR CONTROL

the way it is brought about. He uses for the purpose a cat or dog
whose brain has been removed and whose muscles are therefore
under the influence of the spinal cord alone. Such an animal
exhibits an extraordinary amount of muscular tone, which in itself
indicates that the general influence of the brain is to inhibit the
tonic action of the spinal cord upon the muscles. The animal's
limbs are quite rigid, requiring considerable force to flex the joints,
and when forcibly flexed they spring into the extended position
again as soon as the force is removed. Taking such an animal he
cuts off all the insertions of the flexors of one knee, so they are not
able to exert any force to flex that joint, being careful not to injure
the nerves going to the severed muscles. Then he places the animal
on its back with its limbs pointing upward, and in this position
stimulates by an electric shock the flexors that have had their
tendons cut. The point of the experiment is the surprising thing
that happens. Although the flexors are not able to flex the joint
at all, being cut loose from their attachments, the joint does flex,
just as if they were pulling upon it. The explanation is that the
stimulation of the muscle and its contraction stimulates the sen-
sory endings in it and. a message goes into the spinal cord that
causes an inhibition of the tone of the extensors, whose tonic action
is holding the joint extended, and as soon as they relax the weight
of the limb flexes the joint. As soon as the stimulation ceases
the extensors have their tone return and the joint is extended
again.

Another experiment performed by Sherrington and by others
which indicated the same thing is the stimulation of the pyramidal
cells of the cerebral cortex. When such stimulation is mild and
applied to an area small enough it gives a coordinated movement
involving the contraction of a certain group of muscles and the
relaxation of their antagonists. Stimulation of a similar area
nearby will reverse the action — relaxing the muscles that con-
tracted before and contracting those that relaxed.

To make it appear how such control can be brought about it is
supposed that there are in the formation of synapses two kinds of
brush endings — one kind that has the power to stimulate the
neighboring neurone to action and another kind that has the
power of inhibition. A sensory axone in the cord may, for example,
have some collateral branches with stimulating and some with
inhibiting endings; in this way it gives rise to coordinated action
by stimulating some muscles to action and inhibiting others. The
association neurones, those of the cord and the pyramidal group,
must, if the theory is correct, have both kinds of endings. The
theory has been advanced that a single association neurone of the
cord may have developed upon it just the combination of stimu-

NORMAL MUSCULAR CONTROL

lating and inhibiting endings to give rise to a certain definite
movement, and thus may constitute a "master neurone" for that
movement.

NORMAL MUSCULAR CONTROL.

To see how closely all of these facts and theories apply to the
most common activities of life, think of what happens when we
raise a glass of water to the lips and drink it. No one considers

SPINAL GANGLION CELL

MU1TI POLAR CELL 1
OF ANT HORN-

Fig. 27. — Paths of nerve impulses in voluntary movement. (Halliburton.)

this is a difficult or dangerous feat, yet it requires the use of many
muscles, and every one of them must contract and relax with just
enough force and at just the right time or a catastrophe will result.
First there are the "moving muscles" that raise the arm; they
must contract just enough to allow the water to be poured into the

56 MUSCULAR CONTROL

mouth rather than on top of the head or inside the collar, and must
stop contracting just in time to prevent the glass from striking a
smashing blow against the face. Then there are the "guiding
muscles," which must contract with a force so related on the two
sides as to bring the glass to the lips rather than to the ear or over
the shoulder; the muscles that hold the glass at proper level must
act so as to tip it at exactly the right time in order to spill no water
where it is not wanted ; finally, the muscles that control the glottis
must close the windpipe at just the right moment and prevent the
water from flooding the lungs. In common practice we do all these
things without any attention to details. We simply will to drink
and the nervous mechanism of coordination does the rest.

The mechanism that performs all these marvellous feats of mus-
cular control is not so complex that we need to pass it by as some-
thing beyond our comprehension. It consists simply of motor,
sensory and association neurones acting upon one another through
their synapses. The muscles are all under the direct and perfect
control of the motor neurones, but the latter never stimulate them
to action excepting as they are influenced to do so by other neu-
rones. When we will to take a drink of water the pyramidal neu-
rones of the brain cortex, a group of association neurones subject
to the influence of the will, send messages down the cord to the
motor neurones that control the muscles of the hand and arm to
initiate the movement. As the glass is grasped and raised, sensory
endings in the skin of the hand and in the muscles and joints of
the hand and arm are stimulated by the action. The stimuli thus
produced give rise to sensory impulses that pass up the nerves of
the arm to the spinal cord, where they influence the motor neurones
that are acting to modify their action when the proper time comes
and also influence the neurones controlling other muscles to begin
to act when they are needed. At all stages of the movement these
sensory impulses are acting to guide the muscular contractions of
the next stage. Association neurones of the cord undoubtedly aid
in spreading the effect of the sensory stimuli to the right motor
districts. Just as the pyramidal neurones at the beginning of the
act stimulate some motor groups and inhibit others, so the impulses
coming in from joints, muscles, skin and eyes influence some muscles
to contract and others to relax; each in its turn, and so perfectly
guide the execution of the later phases of the movement.

Most of the bodily movements made by everybody in the course
of every-day life, such as walking, talking, eating, dressing, and the
like, consist of a continuous repetition of comparatively simple
reflex acts, like the one we have been considering; the order and
time of the different acts are, of course, quite as important as the
form of the movements. The nervous mechanism we have just

NORMAL MUSCULAR CONTROL 57

described is evidently just as capable of handling these series of
movements as it is of controlling the separate acts. The incoming
stimuli from the muscles, joints, and skin must be in evidence all
the time to keep the muscles under full control, and stimuli from
the eye frequently. Actions involving poise and balance will
involve the activity of the cerebellum and the semicircular canals
also. There is no apparent reason why the same nervous mechanism
is not able to control the more complex activities of gymnasts,
ball-players, musicians, and other skilled performers.

The question now arises, How do we acquire the ability to per-
form new movements? Up to a certain day a child has never tried
to walk. A week later he walks everywhere. In a single period
of practice one often acquires such an accomplishment as throwing
a curved ball, swimming with the scissors kick, doing the twist
service in tennis or executing the snake in club swinging. How
can one learn in a day or in an hour to do what was impossible for
him to do the day before?

Let us notice first just how we go at it to learn a new exercise.
First, we watch someone do it and try to get a clear idea of how he
does it; we then try to imitate, giving our entire attention to the
performance. The first one or two trials are apt to be failures,
but by comparing the imitation with the original and repeating
the attempt we are apt to improve and soon be able to do the
thing to our satisfaction. Right here is where a teacher is of use —
to give the learner a clear idea of what is to be done in the first
place and then to keep him posted regarding his mistakes as he
proceeds. With persistent practice we soon reach the place where
attention is no longer necessary, the movement gradually becoming
reflex.

To execute a new movement for the first time the pyramidal
cells of the brain must come into action. By their use we can
move any part of the body at will. The first trial is apt to be a
very crude imitation because our idea of the details of the move-
ment is vague and incomplete and hence the attempt to do it is a
step in the dark. We make a movement as nearly as we can like
the pattern and then we try to see how it differs; in each voluntary
trial it is the pyramidal cells that direct the movement by stimu-
lating certain motor neurones and inhibiting others. By this
method of "cut and try" we gradually eliminate the faults and
approach the correct performance. The use of the pyramidal neu-
rones to direct the movements is the special feature of this stage of
the process.

The new movement gradually becomes reflex as practice con-
tinues, which means that the pyramidal cells or "higher level"
nerve mechanism is replaced in control by "lower level" median-

58 MUSCULAR CONTROL

isms, those of muscular sense in particular. When we perform an
old and familiar movement we can recognize it by muscular sense;
that is, we can tell what we are doing by the sensory impressions
arising in the joints and muscles. In this way we can tell with
our eyes shut whether we are walking or running, whether our arms
are swinging alternately or together, and in general we could name
any movement we had just made through the knowledge we have
of it through the muscular sense. We have seen how these same
sensory impulses that give us a sense of position and movement
also guide the performance of reflex acts. But there can be no
muscular sense of a movement we have never made. Such a sense
has to be developed by repeated performance of the movement
with the aid of the pyramidal neurones, and when the correct
movement has been practised long enough to develop a muscular
sense of it, then and not till then can it become a reflex. Much as
the eye has to gradually acquire a knowledge of a wholly new
scene or object, so the muscular sense gradually comes to recognize
a new movement and to be able to control it. Like any other living
thing, a nerve ending develops and its function, which in this case
is response to stimuli, improves with use. This is why athletes,
musicians, and members of some skilled trades and professions can
be so marvellously accurate and sure in the muscular acts they
practise so many thousands of times.

By guiding the new movement through dozens and perhaps
hundreds of repetitions the pyramidal cells cause another impor-
tant change in the nervous structure — development of the synapses
that are most traversed by impulses in the performance of the
movement. We can readily see how a more complete development
of the fine fibrils of the brush-like endings forming each synapse
and a more intimate intertwining of these fibrils together could
make it easier for an impulse to be transmitted. By stimulating
some synapses to greater activity while inhibiting others, the
pyramidal cells promote the growth and development of those
that are most active in the new movement, with the result that
the path thus blazed is ever after easier for impulses to follow.

PART II.

THE UPPEK LIMB.

CHAPTER IV.
MOVEMENTS OF THE SHOULDER GIRDLE.

The shoulder girdle in man consists of two bones, the clavicle
and the scapula. The bones of the arm are joined to the scapula
and the clavicle connects the scapula with the main part of the
skeleton. The clavicle extends horizontally sidewise and slightly
backward from its junction with the top of the sternum and joins
the scapula at the tip of the shoulder. The scapula lies on the
outer surface of the chest at the back, extending, in normal posi-
tion, from the' level of the second rib to that of the seventh, with
its posterior border about 2 inches distant from the spinal column
(Fig. 28). _

The clavicle, which is about 6 inches long, appears straight when
viewed from the front, but when seen from above it is curved like
an italic /, with the inner end convex to the front and the outer
end convex to the rear. The upper surface is smooth and the under
surface rough ; the inner end is the thicker and the outer end more
flattened (Fig. 29).

The scapula is a flat triangular bone with two prominent pro-
jections upon it: the spine from the rear and the coracoid from the
front. The spine has a flattened termination called the acromion.
A deep impression above is named from its position the supra-
spinous fossa, while the shallower one below is called the infra-
spinous fossa. The humerus articulates with a shallow socket at
the outer angle, just below the acromion, which is known as the
glenoid fossa. The greatest length of the scapula in man is from
above downward, in the adult about 6 inches; its greatest breadth
is horizontal, about 4 inches. This is a marked exception to the
general rule in vertebrate animals, most animals having the long
axis of the scapula in line with its spine, so that the glenoid fossa
is at the end of the scapula instead of at the side.

MOVEMENTS OF THE SHOULDER GIRDLE

Fig. 28. — The shoulder girdle, rear view: Sc, scapula; cl, clavicle; Sp, spine of
scapula. (Richer.)

Fig. 29. — Shoulder girdle, front view: Sc, scapula; cl, clavicle; co, coracoid;
A, acromion; st, sternum. (Richer.)

MOVEMENTS OF THE SHOULDER GIRDLE 61

The clavicle is joined to the sternum by a double joint, the two
bones being separated by a cartilage, with one articulation between
the sternum and the cartilage and another between the cartilage
and the clavicle. The cartilage serves as an elastic buffer in case
of shocks received at the arm or shoulder, and the joint permits
the outer end of the clavicle to be moved up and down, forward and
backward, or any combination of these movements ; it also permits
slight rotation of the clavicle on its long axis. The capsular liga-
ment of the joint is strengthened by thickened bands at the front
and rear; injury of the joint is further prevented by a ligament,
called infraclavicular, which joins the two clavicles, and by a liga-
ment called the costoclavicular, which connects the under surface
of each clavicle with the rib below it.

The outer end of the clavicle is joined to the anterior border of
the acromion by a joint permitting considerable movement in vari-
ous directions. The capsular ligament is strengthened on the upper
side, but the main protection against injury to the joint is the
coracoclavicular ligament, a strong band of fibers connecting the
top of the coracoid with the under surface of the clavicle.

All movements of the shoulder girdle may be properly called
movements of the scapula, since the position of the clavicle does
not permit of its moving independently. These movements always
involve both of the joints just described, the clavicle moving so as
to allow the scapula to assume its proper relation to the chest wall.

The movements of the scapula may be classified as follows :

1. Backward toward the spinal column (adduction) and sideward
and forward away from it (abduction) ; this movement may extend
through 6 inches or more, being limited posteriorly by contact of
the two scapulae at the median line and anteriorly by the resistance
of the posterior muscles.

2. Upward movement of the entire scapula (elevation) and down-
ward (depression) ; this may take place through four or five inches.

3. Rotation on a center so as to raise the acromion and turn the
glenoid fossa upward (rotation up) and the reverse (rotation down),
which may take place through an angle of 60 degrees or more.
Rotation of the scapula is associated with all upward and downward
movements of the arm.

Since the clavicle is attached to the sternum, which is compara-
tively stationary, it is evident that the acromion must always
move in a curve with the clavicle as a radius. Since the clavicles
are horizontal in normal position, any movement involving raising
or lowering of the acromion will therefore narrow the distance
between the two shoulders. Since the clavicles normally slant
backward somewhat, evidently all adduction of the scapula will
narrow the shoulders, and abduction will widen them until the

62 MOVEMENTS OF THE SHOULDER GIRDLE

two clavicles fall in one line, after which further abduction will
narrow them again. The action of the clavicle will also cause the
acromion to go toward the rear as the scapula is moved toward
the spinal column.

The following six muscles connect the shoulder girdle with the
main skeleton, hold it in normal position, and give rise to the move-
ments just described. In preparation for the study of such move-
ments as lifting, throwing, pushing, striking, etc., which involve
both arm and shoulder girdle, it is well to make a careful study of
the individual actions of these muscles.

TRAPEZIUS.

The trapezius muscle is a flat sheet of muscular fibers located
on the upper part of the back and lying immediately beneath the
skin.

Origin. — Base of the skull, ligament of the neck, and the row of
spinous processes of the vertebrae from the seventh cervical to the
twelfth dorsal inclusive (Fig. 30).

Insertion. — Along a curved line following the outer third of the
posterior border of the clavicle, the top of the acromion, and the
upper border of the spine of the scapula.

Structure. — Best studied in four parts, passing from above
downward.

Part one is a thin sheet of parallel fibers starting downward
from the base of the skull and then curving somewhat sideward
and forward around the neck to the insertion on the clavicle. It
is so thin and elastic that when it is relaxed one or two finger-tips
can be pushed down behind the outer third of the clavicle with
ease, stretching the muscle before it and forming a small pocket;
when it contracts the fingers are lifted out and the pocket disap-
pears. This enables us to test the action of part one of the trapezius,
which is too thin to be seen and felt in the usual way.

Part two, extending from the ligament of the neck to the acro-
mion, is a much thicker and stronger sheet of fibers, tendinous at
the origin and converging to the narrower insertion.

Part three is similar to part two and still stronger, and includes
the fibers that arise from the seventh cervical and the upper three
dorsal vertebrae; these converge somewhat to the insertion on the
spine of the scapula.

Part four, the lowest, is not so strong as the two middle por-
tions, but stronger than the first; the fibers converge from their
origin on the lower dorsal vertebrae to join a short tendon attached
to the small triangular space where the spine of the scapula ends,
near the vertebral border.

TRAPEZIUS

Action. — A reader who has no anatomical material at hand can
get an idea of some of the conditions under which the muscles work
by study of Fig. 30 and others similar to it, but observation of a
well-mounted skeleton and a living model are necessary to the
best work.

LAST CERVI
CAL VERTEBRA

LAST THORA
CIC VERTEBRA

LAST LUM
BAR VERTEBRA

Fig. 30. — Trapezius and latissimus. (Gerrish.)

It can readily be seen by observation of the skeleton that when
the head is free to move, contraction of part one of the trapezius
will lower the back of the skull and turn it to the side; since the
skull is poised freely on a pivot at its base, this will tilt the chin up
and turn the face to the opposite side. When part one of right

MOVEMENTS OF THE SHOULDER GIRDLE

and left sides contract at once, evidently they will neutralize the
tendency to rotate the head and will tilt the chin up with double
force.

With the head held still and the shoulder girdle free to move,
contraction of this portion will evidently lift the clavicle and
scapula, but with little force, because the muscle is thin and weak.

Action of part two will pull upward and inward, swinging the
acromion on the sternal end of the clavicle as a center, and drawing
it slightly backward or forward, depending on the position of neck
and shoulder at the start.

Fig. 31. — The direction of pull of the four parts of the trapezius on the right and
of the levator and rhomboid on the left: L, levator; R, rhomboid.

Part three pulls in nearly a horizontal line upon the spine of
scapula, drawing it toward the spinal column; the posterior edge of
the scapula will glide along the chest, while the swing of the clavicle
will throw the acromion backward as the scapula is adducted.

Part four pulls so as to draw the vertebral border of the scapula
downward and slightly inward, the lower fibers pulling more
directly downward.

When all the parts of the trapezius contract at once it is impor-

TRAPEZIUS

tant to notice that they act upon the upper rather than the lower
portion of the scapula ; since they at the same time lift the acromion,
adduct the spine, and depress the vertebral border, they must by
their combined action rotate the bone so as to turn the glenoid
fossa upward rather than to move the whole bone in any direction.

The study of cases in which the use of the trapezius has been
lost by paralysis or atrophy verifies the conclusions we have reached
as to its action. Fig. 32 shows how the trapezius rotates the scapula,
as can be observed by comparing its position on the two sides;
the left side, where the muscle is sound, showing upward rotation
while the right side shows the opposite. Fig. 33 shows how the
trapezius influences the posture of the
scapula when the muscles are only
holding the body in habitual posture.
Here the right trapezius is missing,
and the reader will notice how far the
scapula, especially the upper part of
it, is out of normal position because
of its absence; the left side, which is
normal, shows correct position for com-
parison. Such studies, extended over
hundreds of cases, have led to the con-
clusion that it is mainly the third and
fourth parts of the trapezius that are
responsible for holding the scapula back
toward the spinal column and mainly
the second part that keeps it up to
normal height; this is especially true
in unconscious habitual posture.

The stimulation of the trapezius by
electric current also verifies our conclu-
sions as to its action. Stimulation of
part one or part two gives lifting of
the shoulder; stimulation of part three

gives adduction with narrowing and carrying the acromion to the
rear; stimulation of part four gives depression of the vertebral
border with slight adduction; stimulation of all at once give slight
elevation but especially rotation upward. The amount of upward
rotation produced by the trapezius is small — not more than 15 to
20 degrees. The much greater rotation readily seen in raising the
arm up by the head leads us to infer that other muscles can produce
the same movement to a greater extent. The two middle parts
of the trapezius, its thickest and strongest portion, are admirably
fitted to anchor the upper end of the scapula firmly to the spinal
column, so that if the lower angle were drawn forward, extensive
5

Fig. 32. — Subject[lacking right
trapezius, trying to hold shoul-
ders well back. (Duchenne.)

MOVEMENTS OF THE SHOULDER GIRDLE

upward rotation would be produced. The reader will be interested
to watch this point as our study progresses.

Since the trapezius lies immediately beneath the skin it is com-
paratively easy to test its action in various movements by observ-
ing the thickening and hardening of its fibers during contraction.
As shown in Fig. 34 the lower three parts show this effect plainly,
the upper part indistinctly. The upper part of the trapezius illus-
trates well why it is necessary to study the muscles on the living
model.

Fig. 33.-

-Abnormal posture of right scapula due to loss of the right trapezius.
(Mollier.)

We have noticed that the first part of the trapezius is admirably
situated for lifting the shoulders, and that when it is stimulated by
electric current it does so promptly. When we shrug the shoulders,
therefore, it is natural to infer that it aids in the movement, but
observation of the kind we are considering now shows that it does
nothing of the kind, remaining in complete relaxation while the
movement is being performed.

To prove this we need only to press the tips of two fingers down

TRAPEZIUS

behind the outer third of the clavicle and then, while they are
there, to shrug the shoulders. The first part of the trapezius not
only fails to lift the fingers out from behind the clavicle but we
can remove the fingers, while the shoulders are lifted, and see the
deep pocket remaining there. To notice how actual contraction
of the muscle affects it, raise the arm sideward above the level of

Fig. 34. — The trapezius in action. T, trapezius; D, deltoid.

the shoulder and see how quickly the fingers are lifted out and the
pocket obliterated. If the shrugging of the shoulders is done
strongly, against a resistance, the first part of the trapezius acts
in some subjects, but jnot in all; the same is true in taking the
deepest possible oreath.

The reader should not infer from this illustration that a study of
what a muscle can do is no indication of what it will do, for in the

68 MOVEMENTS OF THE SHOULDER GIRDLE

great majority of cases all the muscles so situated as to be able to
help in an exercise do so. There are, however, enough instances
like this one to show that in the nervous control of the muscles in
bodily exercise it is always necessary to supplement the study of
what a muscle might do by noticing what it actually does. These
exceptions to the principle of economy, which is plainly violated
when a muscle that can help perform a movement is left idle while
it is being made, suggest inquiry as to why such exceptions occur.

The nervous mechanism by which we coordinate bodily move-
ments is, like the muscular system, inherited from ancestors, how
far back we do not know. Possibly the first part of the trapezius
is a group of fibers acquired more recently than others. If, as some
scientists believe, man descended from a vertebrate that stood in
the horizontal posture and only acquired the upright posture after-
ward, the present habitual posture of man may call for the use of
some muscles not needed at the time the movement was developed
in the nervous system; some cases will be noted as we progress
that are possible to be explained in this way.

Another peculiarity in the action of the trapezius that should be
noticed through this kind of study is the effect of the posture of
the trunk on the action of parts two and three. When the shoulder
is lifted as high as possible or when a weight is held on the shoulder,
the subject standing erect, part two contracts strongly and part
three slightly if at all; if he does the same thing in a stooping pos-
ture, as when one lifts a pail of water from the ground, parts two,
three, and four all act at once, and the lower parts relax as the
erect position is reached. Here the action meets the need exactly,
and the person unconsciously brings into action the adducting and
the elevating portions when they can do the most good.

All parts of the trapezius come into action at the same time in
raising the arms sideward, and especially in raising them above
the shoulder level, as shown in the above figure. No other bodily
movements seem to employ the whole trapezius at once.

LEVATOR.

This is a small muscle on the back and side of the neck beneath
the first part of the trapezius (Fig. 35).

Origin. — The transverse processes of the upper four or five
cervical vertebrae.

Insertion. — The vertebral border of the scapula, from the spine
to the superior angle.

Structure. — A thick band of parallel fibers, tendinous near the
origin.

LEVATOR

Action. — If the line (see Fig. 31) indicating the direction of pull
of the levator is extended across the scapula it is seen to pass very
nearly through the center of the bone, and therefore the levator
appears to be so situated as to draw the scapula upward and inward

Fig. 35. — Muscles of second layer of the back and those on the back of the
shoulder. (Gerrish.)

as a whole rather than to rotate it. When, however, the levator is
stimulated by electricity it lifts the vertebral edge of the scapula
first and then moves the bone as a whole, giving a combination of
elevation and downward rotation. This is explained by the fact

70 MOVEMENTS OF THE SHOULDER GIRDLE

that the arm weighs down the acromial side of the scapula, and
many muscles joining arm, scapula, and clavicle on that side add
their resistance to any elevation, while the vertebral border is more
free "to move. Study of the living model shows that the levator
and the second or acromial portion of the trapezius do the work
in shrugging the shoulders and lifting or carrying weights in the
hand or on the shoulder, as in case of a hod-carrier, postman, or
ice man. The levator can be felt through" the upper trapezius, and
on a favorable subject one can observe that part two of the trapezius
acts alone when a weight is held in the hand unless the shoulder is
lifted; but as soon as the shoulder is raised by the slightest amount
the levator springs instantly into action. This observation is made
all the more interesting by beginning the movement in stooping
posture and noting the shifting action of the muscles as the body
is raised to the erect position.

The levator is an important support to the scapula in habitual
posture, aiding the second part of the trapezius in holding it up to
normal level. Subjects who have lost the use of the levator have
the shoulder depressed, the deformity being most marked when
both levator and second part of the trapezius are lacking. Loss of
these two main supports gives rise to the type of thin neck and
sloping shoulders that is known as "bottle neck."

RHOMBOID.

The rhomboid is named from its shape, that of an oblique par-
allelogram. It lies beneath the middle of the trapezius( Fig. 35).

Origin. — The row of spinous processes of the vertebrse, from the
seventh cervical to the fifth dorsal inclusive.

Insertion. — The vertebral border of the scapula, from the spine
to the inferior angle.

Structure. — Parallel fibers extending diagonally downward and
sideward from the origin. The upper part, usually separate from
the lower and described separately as the "rhomboideus minor,"
is thin and weak, while the lower part is thick and strong. The
attachment to the scapula is peculiar, the fibers joining a tendon
of insertion that is scarcely attached to the scapula at all for its
upper two-thirds; sometimes the middle half is entirely free from
the edge of the scapula, bringing the pull to bear on the lower angle
alone.

Action. — The structure of the rhomboid and its manner of inser-
tion gives it a line of pull as shown in Fig. 31, considerably different
from what is suggested by its general location and appearance.
Figs. 32 and 36, from Duchenne, show how it adducts the lower
angle of the scapula without adducting the upper angle at all, and

SERRATUS MAGNUS

so rotates the scapula strongly downward. Fig. 32, where the
right trapezius is lacking, shows the combined action of the rhom-
boid and latissimus on the right side. The glenoid fossa is turned
to face considerable downward, and Duchenne states that while
the rhomboid is in contraction the subject cannot raise the arm
above the level of the shoulder.

The part played by the rhomboid in maintaining normal posture,
as shown by defective cases, consists in moderating the upward
rotation of the scapula produced by the trapezius, so as to keep
the acromion down and in holding the lower angle close to the ribs.
Subjects who have lost the use
of the rhomboid have this angle
of the scapula projecting con-
spicuously from the back, with a
deep gutter beneath its edge — a
position due to the pull of muscles
that attach to the upper part of
the bone.

The rhomboid acts powerfully
in all downward movements of the
arms, such as chopping with an
ax, striking with a hammer, pull-
ing down on a rope, and rowing.

SERRATUS MAGNUS.

This muscle, named from its
serrated or saw-toothed anterior
edge, lies on the outer surface of
the ribs at the side, covered by
the scapula at the rear and the
pectoralis major in front. It lies
immediately beneath the skin for
a space a little larger than the hand just below the axilla or arm-
pit, its five lower sections showing plainly through the skin when
the arm is raised against resistance, as in Fig, 39.

Origin. — The outer surfaces of the upper nine ribs at the side of
the chest.

Insertion. — The vertebral border of the scapula, from the spine
to the lower angle.

Structure. — In two separate parts, the upper and lower. The
upper part includes the fibers arising from the three upper ribs
and diverging slightly to be inserted along the whole length of the
scapula below the spine; the lower part is fan-shaped, the fibers
arising from the lower six attachments on the ribs converging to

Fig. 36. — Isolated action of the rhom-
boid. The right rhomboid is contracted
while the left is relaxed. (Duchenne.)

MOVEMENTS OF THE SHOULDER GIRDLE

be inserted together at the inferior angle. The lower part is thicker
and stronger than the upper.

Action. — The fibers of the serratus extend too nearly lengthwise
of the ribs to exert much pull to move them unless the scapula is
raised. Its upper fibers are well situated for drawing the scapula

Fig. 37. — Serratus magnus, subscapularis and teres major. Notice that the clavicle
is cut apart and the scapula turned back away from the chest wall. (Gerrish.)

forward as a whole, with rotation somewhat up or down according
as to which fibers shorten most. As this motion takes place through
the 5 or 6 inches of its extent the swing of the clavicle on the ster-
num will evidently cause the acromion to move outward slightly
and then inward, the two shoulders approaching each other rapidly

SERRATUS MAGNUS

as the clavicles come forward to the farthest possible point. The
lower part of the muscle is in a position to produce vigorous rota-
tion upward by drawing the inferior angle of the scapula forward.
Notice how well these lower fibers are placed to associate with the
trapezius in turning the glenoid fossa upward.

Stimulation of the serratus magnus verifies these conclusions,
and study of defective cases also supports them. Loss of the ser-
ratus has little effect on habitual posture of the scapula, but it
interferes seriously with forward movements of the shoulder and

Fig. 38. — Effect of loss of serratus on posture of the scapula during elevation of the
arms. Left side normal. (Mollier.)

arm. Subjects lacking the serratus cannot lift the arm higher
than the shoulder, and when they try to do so the posterior border
of the scapula projects backward instead of lying close to the chest
wall, as it does when the serratus acts normally in the movement.
Fig. 38 shows the deformity occurring in such cases, the normal left
side contrasting with the right, where the serratus is lacking.

Study of the serratus on the normal living body shows its action
in a very clear and interesting way. Whenever the subject pushes
or reaches forward the scapula can be seen and felt to glide forward

74 MOVEMENTS OF THE SHOULDER GIRDLE

over the surface of the chest, and the distance it moves is surpris-
ing to all who have not observed it before. When the arms are
raised the trapezius can be seen and felt to contract as soon as they
begin to move, but the lower serratus does not begin to contract
until they have been raised through at least 20 degrees and some-
times through 45 degrees. This can be tested by placing the fingers

Fig. 39. — The lower part of the serratus magrras in action. The saw-toothed
shape of its lower front margin is shown plainly where it attaches to the ribs. . Only-
five saw teeth show, the upper ones lying beneath the pectoralis major.

on the lower angle of the scapula and noticing when it begins to
move forward. Why the nervous system, in controlling the muscles
in this movement, should leave the lower serratus idle at the
beginning is a puzzling question, but it persists in doing so in all
subjects, even when the rotation of the scapula is made especially
difficult by loss of the trapezius.

PECTORALIS MINOR 75

Another interesting case in which the lower serratus fails to act
when it would be of use is when a weight is lifted or carried on the
shoulder. Although the lower serratus can lift the acromion with
great force, as we have seen, it never acts in lifting with the shoul-
der or carrying a heavy weight on it, the work in this case being
done by the middle trapezius and levator so long as the arm hangs
at the side. As soon as the arm is raised 30 degrees or more from
the side it at once springs into action. This shows a reason why
one who carries a heavy weight on the shoulder finds it restful to
hold the arm in various positions — sometimes down by the side
and sometimes raised.

PECTORALIS MINOR

A small muscle located on the front of the upper chest, covered
by the pectoralis major.

Origin. — The outer surfaces of the third, fourth and fifth ribs at
a point a little sideward from their junction with the costal carti-
lages (Fig. 40).

Insertion. — The end of the coracoid.

Structure. — Three groups of nearly parallel fibers that converge
to join a single small tendon at the upper end.

Action. — Ihe line of pull of the pectoralis minor may be repre-
sented on a mounted skeleton by a rubber band stretched from the
coracoid to the fourth rib at a point about an inch from its junc-
tion with the costal cartilage. When the scapula is in normal
position the direction of pull on the coracoid will be seen to be
forward, downward and inward at nearly equal angles. The inward
pull is prevented from acting on the scapula by the position of the'
clavicle, so that contraction of the muscle is calculated to produce
a combination of abduction and downward rotation of the scapula.
It can also be seen that the pull of the pectoralis minor, by prying
across the chest, tends to lift the posterior edge and especially the
lower angle of the scapula away from the ribs.

When the scapula is held still it is evident that action of this
muscle will lift on the middle ribs, especially when the shoulder is
raised in preparation for it, as one unconsciously does in taking a
deep breath.

While normally the pectoralis minor is deeply covered, Duchenne
reports cases in which, because of complete atrophy of the pec-
toralis major, it lay immediately under the skin and could be stim-
ulated by electric current. The isolated action secured in this way
is the same as that stated above. It is possible in favorable sub-
jects to feel the contraction of the pectoralis minor through the
muscle that covers it by proceeding as follows: have the subject

MOVEMENTS OF THE SHOULDER GIRDLE

hold the arms close to the sides and a little to the rear, which inhib-
its any action of the pectoralis major; then have him inhale deeply,
first lifting the shoulders slightly. This puts the pectoralis minor
into vigorous action and its lateral swelling may be felt and even
seen as it lifts the relaxed tissue covering it.

Fig. 40. — The pectoralis minor and subclavius. (Gerrish.)

To summarize, it may be said that the pectoralis minor acts in
deep and forced breathing, but probably not in quiet breathing; it
is placed in a position to help in all movements involving abduc-
tion and downward rotation of the scapula, which occurs in strik-
ing forward and downward as in chopping and also in supporting
a part of the body weight on the arms. In most of these cases actual
test of its action is rendered impossible because of the contraction
of the large muscle covering it.

SUBCLAVIUS.

The smallest of this group of muscles; located, as its name indi-
cates, beneath the clavicle.

Origin. — The upper surface of the first rib, just where it joins its
cartilage.

POSTURE OF THE SHOULDERS 77

Insertion. — A groove extending along the middle half of the
under side of the clavicle.

Structure. — Fibers radiating fanwise from the small tendon of
origin to the much wider insertion.

Action. — The action of the subclavius can only be inferred from
its position, as it is not readily felt nor stimulated from without.
It is in a position to depress the clavicle, and the long outward
slant of its fibers makes it also draw inward, lengthwise of the
clavicle — a pull that can serve to protect and strengthen its joint
with the sternum in such movements as hanging by the hands,
where the weight of the body tends to pull the shoulder girdle
from the main part of the skeleton.

POSTURE OF THE SHOULDERS.

The shoulder girdle is so freely movable that its habitual posi-
tion depends on the relative tension of the six muscles we have been
studying, together with some influence produced by two others
that act indirectly on it through the arm. Whenever some of
these muscles are absent or inactive because of disease, when the
clavicle or scapula is deformed by disease or accident, or when any
of the muscles fail for any reason to exert the right amount of
tension, an abnormal posture of the shoulders is apt to result.

It is generally assumed by anatomists, as previously stated, that
for normal posture of the shoulder girdle the clavicles should be
approximately horizontal, which places the scapulae at a height
extending from the second to the seventh rib; that the scapulae
should be 4 inches apart, 2 inches on each side of the median line;
and that they should lie flat against the chest wall on the back.
Hygienists and artists have been inclined to accept this view, and
it seems a reasonable ideal to hold.

The most common defect in the position of the shoulder girdle
is abducted scapulae. This is objectionable from a hygienic stand-
point, partly because it weakens the support which the coracoid
should give to the pectoralis minor and thus does away with the
tension that muscle should exert on the ribs. The amount of assist-
ance really given by the pectoralis minor in holding the chest up
in an expanded position is not known, but it is commonly assumed
that it helps. Another and perhaps greater objection to abducted
scapulae is that it is usually seen associated with drooping head
and collapsed chest in the position known as "round shoulders."
This fault of posture will naturally be studied when we take up
the movements of the spinal column, but the part played by the
shoulder girdle is of interest here. The weight of arm and scapula
probably help to depress the chest.

78 MOVEMENTS OF THE SHOULDER GIRDLE

Abduction of the scapula, as a fault of posture, most often
results from continuous occupation with the arms held in front of
the trunk. In writing, sewing, holding a book in position to read,
and numberless other occupations, the arms and shoulders are held
forward by continuous contraction of the serratus, pectoralis major
and minor, while the trapezius, rhomboid and levator are relaxed
to permit the scapulae to move forward. This gradually tends to
increase the bulk, strength, and tone of the muscles on the front
and to modify their development so as to make them permanently
shorter, while it has the opposite effect on the back group. After
a time the scapulae can be brought to normal position with diffi-
culty, and this difficulty gradually becomes greater until the normal

Fig. 41. — "Neck firm," an exercise used in Swedish gymnastics for correction of
habitual abduction of the scapulae.

position is impossible. All this can be prevented by the regular
practice of exercises that will develop, shorten and increase the
tone of the trapezius, levator and rhomboid, and at the same time
put on a stretch the muscles that are becoming shortened.

It is plainly one of the duties of a system of school gymnastics
to give daily some good corrective to oppose the deforming ten-
dency of school occupations. A very few of the most efficient
exercises should be used frequently, and a greater variety of others
that tend in the same direction should be taught as the time goes
on, including as many as possible that are recreative as well as
corrective. Among the best exercises for daily use may be men-
tioned the Swedish exercise "neck firm," shown in Fig. 41. The

POSTURE OF THE SHOULDERS

arms are raised sideward until slightly above the level of the shoul-
ders and then the elbows are bent and the finger-tips placed against
the back of the neck, which is held vigorously erect; the elbows
are held back strongly. The position is held long enough to ensure
an accurate position and complete contraction of the trapezius,
then the arms are returned to the sides through the same path
and the movement repeated several times. Raising the arms side-
ward and upward to the position of Fig. 63 is also good for correct-
ing the posture of the shoulders, but in taking it there should be
care not to thrust the chin forward by too vigorous action of the
upper trapezius. Another good exercise is drawing the shoulders
back and turning the palms out, as shown in Fig. 76.

Fig. 42. — "Chest firm," a corrective exercise for abduction of the shoulders.

Shoulder braces, such as are often advertised and used to cor-
rect such faults, may be beneficial or highly injurious according to
the manner of their use. The good they may do is to stretch the
shortened muscles on the front of the chest and relieve the trapezius
from extreme fatigue and prolonged stretching during an occupa-
tion conducive to the defect. The harm they are apt to do when
used without intelligent directions is to leave the weak muscles
that should maintain good posture without any necessity for vigor-
ous action and thus weaken them still more. All such contrivances

MOVEMENTS OF THE SHOULDER GIRDLE

for the support and relief of overworked muscles should be used
only under the direction of a competent specialist, and in practi-
cally all cases should be supplemented by exercises that will tone
up and develop the weak muscles. In case of complete loss of the
use of a group of muscles the brace may be needed permanently,
but in any case expert advice should be secured.

Fig. 43,. — Upward stretching of one arm and downward stretching of the other
arm, used for correcting uneven height of shoulders.

A marked projection of the lower angle of the scapula, often
known as "winged scapula," is usually due, as has been already
observed, to a deficiency in the action of the rhomboid and short-
ening of the pectoralis minor. In mild cases the exercise of Fig.
76 is a good corrective, the effort to hold the elbows down giving
vigorous but not straining work for the rhomboid while the effort
to hold the hands back will stretch the pectoralis minor. As a

POSTURE OF THE SHOULDERS 81

general principle it is well to remember that exercises involving
elevation of the humerus give work for the trapezius rather than
the rhomboid, while the reverse is true of exercises involving depres-
sion of the humerus. A further study of this point will be made
in the next chapter.

Uneven height of shoulders is a defect of posture often associated
with lateral curvature of the spine. When the spinal column is
straight and the fault is simply a lowering of one shoulder from
lack of tone of the trapezius and levator, persistent shrugging of
that shoulder is often sufficient to correct it. Another effective
corrective for such a fault is upward extension of the arm on the
low side combined with downward extension of the other arm, as
shown in Fig. 43. This exercise is conveniently practised in alter-
ation with the one shown in Fig. 41.

QUESTIONS AND EXERCISES.

1. Pick out a clavicle from the bones of a dismembered skeleton; point out and
name its two ends, two surfaces, two borders, and two articular surfaces; tell whether
it is a right or left clavicle.

2. Pick out a scapula from the bones of a dismembered skeleton; point out and
name its two prominent projections, its two surfaces, three angles, three borders,
three principal depressions, and two articular surfaces; tell whether it is a right
or left scapula.

3. Demonstrate and name the six movements of the scapula, with the names of
the muscles producing each.

4. Describe four different ways of studying the action of a muscle, and explain
the advantages of each.

.5. Explain how a weak trapezius may cause flattening of the front of the chest,
and why the rhomboid cannot assist in correcting the defect.

6. If a man whose work is pushing a lawn mower wishes to take exercise to pre-
vent its causing faulty posture of the scapulse, should he be advised to box, put the
shot, row, or drive a fast horse?

7. By means of a ruler or tape, measure the distance a subject can move the
tip of the shoulder forward and back without moving the trunk; how far he can
move it up and down; how much he can vary the width across the shoulders.

8. Mark on the skin with a flesh pencil the location of the subject's vertebral
border of scapula while in habitual position; repeat when he is reaching forward as
far as possible; when his scapulae are adducted as completely as possible. Measure
the extent of movement.

9. In similar manner mark and transfer to paper the angle of rotation of the
scapula that takes place during elevation of the arms from the sides up to vertical
position. Measure the angle with a protractor.

10. Demonstrate on a living model the failure of the first part of the trapezius
and the lower serratus to help in lifting a weight on the shoulder, and the effect of
elevation of the arm on their action.

CHAPTER V.
MOVEMENTS OF THE SHOULDER-JOINT.

The shoulder-joint, formed by the articulation of the humerus
with the scapula, is the most freely movable of the ball-and-socket
joints. The shallow glenoid fossa is deepened by a cup of carti-
lage, the glenoid cartilage, attached firmly to the inner surface of
the fossa, and the head of the humerus fits into the cup. The joint
is surrounded by the usual capsular ligament, which is reinforced
on the front side by a strong band of fibers connecting the humerus
with the coracoid and called the coracohumeral ligament. Sev-
eral tendons of muscles have an intimate relation to the capsule
and add materially to its strength. The capsule is so loose that it
permits the head of the humerus to be drawn out of the socket
about 2 inches, but the tendency of the weight of the arm to pull
it far out is resisted normally by atmospheric pressure and by the
tone of the muscles. The joint is protected by the acromion,
which projects over it, by the coracoid in front, and by the coraco-
acromial ligament, which connects these two processes.

Starting from the resting position at the side of the thigh, the
arm can be raised (elevation or abduction) through movement in
the shoulder-joint, in various directions and to various heights.
The joint permits the greatest elevation toward the front, where it
may swing through 120 degrees; the possible extent of this move-
ment diminishes as we pass backward, being about 90 degrees
when it is directly sideward and 45 degrees directly to the rear.
Further elevation toward the rear is prevented by tension of the
coracohumeral ligament; toward the side or front, by contact of
the greater tuberosity of the humerus and the tendon of the supra-
spinatus muscle with the top of the glenoid fossa. The way in
which the joint limits farther upward movement is shown in Fig. 44.
The reader can observe, by the use of a free humerus and scapula,
how this takes place and can also notice why the arm can be raised
higher toward the front or when the humerus is rotated outward.
First hold the humerus and scapula as they would be when the arm
is at the side; then raise the humerus as in arm elevation side-
ward through 90 degrees and see how the tuberosity hits the top
of the socket; now rotate the humerus 90 degrees to the rear, as
in turning the palm up from this position, and see how the tuber-
osity is carried to the rear over the rounded edge of the socket to

MOVEMENTS OF THE SHOULDER-JOINT

a place where it no longer prevents elevation of the humerus.
Go back to starting-point and observe that elevation forward,
with palms toward each other, does not cause the tuberosity to
meet any solid obstruction.

Having been raised from the side, the arm can be swung for-
ward (flexion of shoulder-joint) until it strikes the front of the chest,
swung backward to the lateral plane (extension) and 20 to 30
degrees back of the lateral plane (overextension). Movement of
the arm downward toward the side from these positions is called
adduction or depression. The shoulder-joint also permits the arm
to describe a circle with the hand (circumduction), turn in or out
on an axis passing lengthwise of the humerus (rotation), and with
upward rotation of the scapula it can be carried up to a vertical
position.

BICEPS.
CORACOACROMIAL \ GLENOID LIGAMENT.
LIGAMENT.
DELTOID.

DELTOID. SUPRASPINATUS.

TERES MAJ

SUB-
SCAPULA-
RS.
LONG HEAD
OF TRICEPS.

teres major. Circumflex vessels.

Circumflex vessels.

SCAPULARIS.

Fig. 44. — Vertical section through the right shoulder-joint, seen from the front,
showing how sideward elevation of the arm is limited to 90 degrees. (Gray.)

Movements of the shoulder-joint are produced by nine muscles
having that as their main function, along with one other (triceps)
which acts on the shoulder- joint with one of its parts while its
main action is upon the elbow-joint. The latter muscle will be
described in the next chapter; the nine are conveniently placed in
three groups of three muscles each. Three of the nine are large
muscles, placed above, in front, and at the rear; with each of these
goes a small associate and a rotator of the humerus, as follows:

Large muscles. Small associates. Rotators of humerus.

Above . . . Deltoid Supraspinatus Infraspinatus

Front . . Pectoralis major Coracobrachialis Subscapularis

Rear .... Latissimus Teres major Teres minor

MOVEMENTS OF THE SHOULDER-JOINT

SMALL
TUBEROSITY

DELTOID.

A triangular muscle located on the shoulder, with one angle
pointing down the arm and the other two bent around the shoulder

to front and rear (Figs. 30, 46
and 48).

Origin. — Along a curved line
following the outer third of the
anterior border of the clavicle,
the top of the acromion, and
the posterior border of the
scapular spine.

Insertion. — A rough spot on
the outer surface of the hu-
merus just above its middle.

Structure. — In three parts —
front, middle, and rear. The
front and rear portions are
simple penniform while the
middle is more complex. The
tendon of insertion divides
near the humerus into five
strands; the outer two, placed
front and rear, receive the
fibers of the front and rear
portions of the muscle, which
arise directly from the bones
above; the middle has four
tendons of origin passing down
from the acromion and the
three tendons of insertion
passing up from below alter-
nate between them ; the mus-
cular fibers of the middle por-
tion pass diagonally across
between the seven tendons.
The result of the arrangement
is that the middle part has
more power and less extent of
contraction than the other two
parts.
Action. — One can study the conditions under which the deltoid
acts by attaching a rubber band to the humerus of a mounted skele-
ton and holding the free end of the band at the various points of
origin in turn. Observe that its most anterior fibers pull upon

EXTERNAL
CONDYLE

MUSCULO-
SPIRAL GROOVE

INTERNAL
CONDYLE

Fig. 45. — The right humerus, front view.
(Gerrish.)

DELTOID 85

the humerus at a fairly large angle (15 to 20 degrees) and that
this angle of pull diminishes as we pass back to the acromion,
where the pull is almost directly upward in line with the humerus;
farther back the angle is greater again. This shows why the middle
needs a more powerful structure than the other parts.

Fig. 46. — The deltoid in action.

Giving the rubber band a tension we can see in what direction
any strands of fibers will move the arm; forward, then outward
diagonally, then sideward, and finally backward, as we pass from
front to rear as before. By using two rubber bands to represent two
strands with origins separated at different distances we can see
how the combined action of different parts raises the arm at every
possible angle and also guides its motion in a definite direction;
by holding the humerus up to the horizontal plane we can see how
various parts pull forward or back upon it.

MOVEMENTS OF THE SHOULDER-JOINT

Using a non-elastic cord to represent a portion of the muscle,
noting its length when the arm is at the side and again when it is
raised to horizontal, we can see how far the muscle must contract
to raise it as far as the joint permits. It is easy to demonstrate in
this way that the middle part shortens less to lift the arm through
90 degrees than the others, the figures being approximately 1^
and 2 inches, from which the fibers of the middle part would

appear to be about 3 inches long
and the front and rear fibers
about 4 inches.

Isolated action of the deltoid,
as described by Duchenne, lifts
the arm just as the above study
of conditions would lead us to
expect; it is raised to the great-
est height by the most anterior
fibers, and when the electric
terminals are moved along the
muscle from front to rear the arm
swings to the rear and gradually
lowers, the posterior fibers being
able to lift it backward but 45
degrees. Anatomists who judged
of the action of muscles solely
by the conditions apparent on
the skeleton or cadaver had for
a long time doubted the ability
of the middle deltoid to start the
elevation of the arm without the
aid of other muscles, because of
its small angle of pull, but Du-
chenne's experiments on isolated
action solved the problem defi-
nitely, showing that it can do so.
When the deltoid contracts from
electric stimulus it does not lift
the arm as high as the shoulder-joint would permit, because the
scapula, being somewhat free to move, is rotated downward by
the pull of the deltoid and the weight of the arm, bringing the lower
angle back well toward the spinal column, depressing the acromion,
and making the posterior edge of the scapula stand out from the
chest wall as in Fig. 38. This downward rotation of the scapula
gives the appearance of only a partial movement in the shoulder-
joint, even when it has been performed to its full extent, precisely
as in attempts to raise the arm by those whose trapezius and ser-

Fig. 47. — Identity of isolated action
of deltoid (left side), with voluntary
attempt to raise the arm when the
trapezius and serratus magnus are
lacking (right side). (Duchenne.)

DELTOID 87

ratus are destroyed. Duchenne shows in Fig. 47 an experiment
to make this plain. The subject has lost the trapezius and serratus
through disease. When he tries to raise his arm he can bring into
action only the deltoid, possibly aided by the supraspinatus. In
the picture he is trying to raise his right arm and at the same time
the left deltoid is being stimulated by electricity. The effect is
the same on both sides: partial elevation of the arm, downward
rotation of the scapula, and a deep trough between the posterior
border of the scapula and the back. Notice how the arm and the
axillary border of the scapula have moved away from each other,
and recall that in normal elevation of the arm the axillary border
moves forward because of the pull of the lower serratus, which
contracts along with the deltoid and trapezius in all normal arm
raising.

Loss of one or more of the three portions of the deltoid interferes
so seriously with all movements involving elevation of the arm that
subjects with this defect have much difficulty in feeding and dressing
themselves. Loss of the posterior deltoid makes it impossible to
put the hand behind the body at the waist line; if it is the front
part the subject cannot bring his hand up to his face or put on his
hat without bending the head far forward ; if it is either the front
or middle portion the arm cannot be lifted above the shoulder level
in any direction. Few muscles are so important to the most
common movements of the arm as the deltoid.

The deltoid is one of the easiest and most interesting muscles to
study on the living body, and no student of kinesiology should fail
to observe its action repeatedly, and upon several different sub-
jects if possible. Since the deltoid raises the arm with such ease
it is well to have the subject make the movements against a resist-
ance great enough to bring it into strong contraction. Such a
resistance can be furnished by a weight in the subject's hand, by
the use of a pulley machine, common in most gymnasia, or by the
hand of the observer.

The anterior deltoid hardens and swells out in all exercises in
which the arm is raised or swung forward against a resistance ; the
middle deltoid does the same when the movement is sideward;
the posterior part when it is backward. The position of "neck
firm" (Fig. 41) brings all three portions into action, providing the
subject holds his elbows well back. All positions above the hori-
zontal bring both anterior and middle portions into action. It is
easy to notice that a wider group of fibers contract in lifting a
heavy weight than in lifting a light one; also that both front and
middle portions come into action before the shoulder level is reached
if the load is heavy. It is also easily seen that with quick arm
elevation the deltoid contracts suddenly and then relaxes, leaving
the momentum of the arm to finish the movement.

88 MOVEMENTS OF THE SHOULDER-JOINT

SUPRASPINOUS.

A small but relatively powerful muscle filling the supraspinous
fossa and covered by the second part of the trapezius (Figs. 35
and 65).

Origin. — The inner two-thirds of the supraspinous fossa.

Insertion. — The top of the greater tuberosity of the humerus.

Structure. — Penniform, the fibers arising directly from the bone
and joining the tendon of insertion obliquely as it passes. through
the center of the muscle, much as the seeds of a pine cone join
their stem.

Action. — The supraspinatus pulls on the humerus with a short
power arm and at a large angle; since it joins the humerus above
the axis while the load is below it, it uses the humerus as a lever
of the first class. Since the power arm is the line from the insertion
to the axis it is plain that the power and weight arms are not in a
straight line here, but the lever is bent sharply at the axis. This
of course has no effect on the action of the muscle or its lever
except to give it a favorable angle of pull.

Isolated action of the supraspinatus, which can be brought about
by stimulating its nerve, raises the arm diagonally outward, but
the direction is not fixed, and the arm may be moved forward or
backward by the observer while the muscle is in contraction with-
out hurting the subject. It is powerful enough to lift the arm to
its full height, even when the deltoid is lost, but it is soon fatigued
when so much work is put upon it. It pulls the head of the humerus
directly into the socket and so prevents the upward displacement
which the pull of the deltoid tends to produce. It is for this reason
that persons who have lost the supraspinatus cannot do much work
involving elevation of the arm, because of the friction of the head
of the humerus against the under side of the acromion. Being
covered by a muscle that usually contracts at the same time it is
not easy to study the supraspinatus on the normal living body.

PECTORALIS MAJOR.

A large fan-shaped muscle lying immediately beneath the skin
over the front of the chest.

Origin. — The inner two-thirds of the anterior border of the
clavicle, the whole length of the sternum, and the cartilages of
the first six ribs, near their junction with the sternum.

Insertion. — By a flat tendon about 3 inches wide into the ridge
that forms the outer border of the bicipital groove of the humerus,
extending from just below the tuberosities nearly down to the
insertion of the deltoid.

PECTORALIS MAJOR

Structure. — The fibers arise directly from the bone and converge
to join the tendon of insertion. Near its insertion it is twisted
through 180 degrees, the lower part passing beneath to be inserted
near the head of the humerus while the fibers from the clavicle
pass across them on the outside and join the humerus lower down.

mk*. %

PECTOR|US;

., E LIQUUS

EXTERN US

'AB'OOM I N I S

Fig. 48. — Deltoid and pectoralis major. (Gerrish.)

Action. — The pull of the uppermost fibers of the pectoralis major
differs from that of the anterior deltoid only in having an origin a
little farther to the front and an insertion a little higher. As we
observe the pull of the different strands in turn passing down-
ward it is plain that when the arm is at the side the whole muscle
is in a position to pull it forward, the upper fibers tending to raise
it and to pull at a better angle as the arm swings forward while the

MOVEMENTS OF THE SHOULDER-JOINT

lower fibers pull at a small angle that grows smaller as the arm
advances, the most of the force acting to pull the head of the
humerus out of its socket. When the arm is first raised to hori-
zontal the angle of pull is greater and a point can be found near
the front horizontal where the pectoralis major pulls at a right angle,
the upper part acting directly forward and the lower part forward
and downward. With the arm overhead all parts pull forward and
downward. The position of the insertion enables it to rotate the
humerus inward ; the twisting of the tendon gives the upper fibers
the longer and the lower the shorter leverage.

Duchenne's study of isolated action cleared up several points
about the action of the pectoralis major which had hitherto been
topics of dispute and showed for the first time just what the muscle

Fig. 49. — The pectoralis major in action. P, pectoral; D, deltoid; S, serratus magnus.

can do and what it cannot do. He shows that it acts like two
muscles, just as the deltoid acts like three and the trapezius like
four. He finds that the upper half of the pectoralis major swings
the arm forward and inward and at the same time lifts the acromion
so that it can help the levator and second trapezius in lifting and
holding a weight on the shoulder; it presses the arm firmly against
the side and front of the chest. When the arm is first raised to
horizontal the action of the upper half swings it horizontally for-
ward ; when it is in vertical position upward the same fibers depress
it forward to the horizontal. Isolated action of the lower half
swings the arm forward and downward, depresses it if elevated,
and pulls the head of the humerus strongly out of the glenoid cavity,
at the same time lowering the acromion and pressing the arm
forcibly against the front and side of the chest.

CORACOBRACHIALIS 91

Loss of the pectoralis major disables one much less than loss of
the anterior deltoid, excepting in movements where great force is
required. When the deltoid is intact the subject can raise his
hand to any position in front of the trunk, fold his arms, place
the hand on the opposite shoulder, etc., even if the pectoralis major
is lacking; the force of gravitation enables him also to lower the
arm to or through any position with the aid of the deltoid; but
the power in forward and downward movements of the arm is
lacking unless the pectoralis can help.

Dr. Beevor, of London, has described an excellent way to begin
the study of the pectoralis major on the living body. First have
the subject hold his arms forward a little below the horizontal and
with elbows extended press his palms strongly together; this brings
the whole muscle into vigorous action and the two parts can be
seen and felt plainly, the tendon standing out in strong relief near
the arm. Now while the subject is doing this let the observer
press down on the extended arms and have the subject resist the
pressure; this instantly causes relaxation of the lower half while
the upper half springs out in still stronger action; if the observer
lifts against the arms and the subject resists, the upper half relaxes
and the lower half acts. Let the observer try to move the subject's
arms alternately up and down while the subject tries to keep them
still, and notice the rapid change of action by watching the tendon
near the arm. Observe that both parts of the muscle contract in
all exercises where there is forward movement of the arms at a
certain level, such as pushing a lawn mower; the upper part works
alone when the movement is upward, as in putting the shot, throw-
ing overhand, and the like ; the lower part acts alone in such move-
ments as sawing or shovelling. Notice how plainly the upper half
shows action in lifting with arms forward, as when a waiter carries
a heavy tray; notice also how it fails to act and the deltoid has it
all to do if the arms are separated too widely; see if you can locate
the width of arms at which the pectoralis ceases to aid the deltoid
in lifting the arms. This is why the shot-putter finds it an advan-
tage to extend the arm in a direction considerably inward rather
than straight forward. He wants the deltoid to have the assistance
of the pectoralis, and in the position of the arm where the latter
works with the best leverage.

CORACOBRACHIALIS .

A small muscle named from its attachments and located deep
beneath the deltoid and pectoralis major on the front and inner
side of the arm (Fig. 50).

Origin. — The coracoid.

MOVEMENTS OF THE SHOULDER-JOINT

Insertion. — Inner surface of the humerus, opposite the deltoid.
Structure. — The fibers arise from a short tendon and are inserted
directly into the humerus. Attachment to the tendon is penniform.

Fig. 50. — Muscles on the front of right shoulder and arm. (Gerrish.)

Action. — Observation of a cord placed to represent this muscle
will convince the reader that it can pull upward and inward on
the humerus, the angle being small and the force mostly used to
lift the humerus lengthwise. Isolated action of the coracobrachialis
holds the humerus strongly upward and swings it feebly inward.

LATISSIMUS 93

It is too deeply placed to make a study of its normal action easily,
but it is believed, because of the facts just stated, to work with
the pectoralis major and the two muscles next following, all of
which pull down on the humerus and thus tend to draw it out of
its place in the glenoid cavity in vigorous downward movements
of the arm.

LATISSIMUS.

A very broad muscle, as its name indicates, situated on the lower
half of the back and lying immediately beneath the skin except for
a small space, where it is covered by the lower trapezius (Fig. 30) .

Origin. — The spinous processes of the six lower dorsal and all
the lumbar vertebrae, the back of the sacrum, the crest of the ilium,
and the lower three ribs.

Insertion.— The bottom of the bicipital groove of the humerus,
by a flat tendon attached parallel to the upper three-fourths of the
insertion of the pectoralis major.

Structure. — The fibers converge from their wide origin much like
the pectoralis major, and like the latter its flat tendon is twisted
so that the upper fibers go to the lower insertion, and vice versa.
The muscle is joined to the lower vertebras and the sacrum by a
sheet of fibrous tissue called the lumbar fascia, which also gives
attachment to several other muscles.

Action. — The latissimus is situated so as to pull the arm down
toward the side from any position of elevation. The lower fibers
are in a position to act to best advantage when the arm is high,
pulling at a right angle when it is near the horizontal, and in doing
so they will tend to depress the acromion ; the short lever arm makes
them adapted for speed rather than power. When the arm has.
been lowered to within 45 degrees from the side the upper fibers
pull at a better leverage than the lower, tending to adduct the arm
and also the scapula, and having a longer lever arm than the lower
fibers. The muscle working as a whole has its best leverage at
about 45 degrees of elevation of the arm, when it pulls at a right
angle; it pulls the arm to the rear of the lateral plane, in a certain
degree of opposition to the lower pectoral, which pulls it forward.
Its insertion on the front of the humerus makes it a rotator inward,
and its position to the rear of the trunk enables it to turn it farther
than the pectoralis major.

Isolated action of the latissimus produces exactly what we would
expect. The upper fibers adduct the scapula so accurately and
strongly that Duchenne is inclined to place it among the muscles
maintaining normal posture of the shoulder girdle, and gives evi-
dence from defective cases to support the opinion. He shows also
that when the lower fibers contract with the arm at the side they

94 MOVEMENTS OF THE SHOULDER-JOINT

draw the head of the humerus down from the socket as far as the
capsule will permit.

Loss of the latissimus results in a forward displacement of the
shoulder, due to the pull of the pectoral muscles, major and minor.
It noticeably weakens all downward movements of the arm. When
both the latissimus and pectoralis major are lost the shoulder is
apt to be too high, because of the unbalanced action of the trapezius
and rhomboid.

Fig. 51. — The latissimus in action. The subject is depressing his arms against
resistance. Notice the narrow upper end of the latissimus just below the arm and
trace its upper and lower margins as it widens out. L is near its center; D, deltoid;
T, long head of the triceps.

The latissimus may be observed on the living body to act vigor-
ously in all strong downward movements of the arms, such as chop-
ping, striking with &r hammer, and in supporting the weight of the
body on the hands; the same is seen in movements more directly
to the rear, such as rowing, paddling, and exercises on chest weights
when the subject is facing the machine. It also acts in raising the
trunk when it is inclined slightly forward up to the erect military
position. The use of the latissimus in this movement is liable to
give an excessive hollow in the back at the waist line unless other
muscles are used to counteract it.

TERES MAJOR

TERES MAJOR.

A small round muscle lying along the axillary border of the
scapula, named "larger round" in comparison with the teres minor
or "smaller round muscle" (Figs. 35, 37 and 50).

Origin. — The outer surface of the scapula at the lower end of its
axillary border.

Insertion. — The ridge that forms the inner border of the bicipital
groove of the humerus, parallel to the middle half of the insertion
of the pectoralis major.

Fig. 52. — The teres major and rhomboid in action. T, teres major; R, rhomboid.

Structure. — Fibers arising directly from the scapula and inserted
into the tendon in a penniform manner.

Action. — The teres major is in a position to pull the humerus
and the axillary border together, and therefore is the most direct
antagonist of the deltoid. It pulls at a right angle when the humerus
has been moved from the side about 45 degrees. The position of
its insertion enables it to rotate the arm inward. When there is a
strong resistance to depression of the arm the action of the teres
major tends to draw the lower end of the scapula forward — a
movement that the rhomboid is in a position to prevent when it acts
at the same time.

96 MOVEMENTS OF THE SHOULDER-JOINT

Isolated action of the teres major, in the words of Duchenne,
" brings the. inner side of the arm and the axillary border of the
scapula toward each other, raises the tip of the shoulder, and car-
ries the arm a little to the rear. The arm and scapula are drawn
together with great force, but the arm is depressed but feebly; it
requires but little strength to lift the arm to the horizontal in spite
of its action." He goes on to say that in cases of loss of the trapezius
he was able to apply electric stimulus to the rhomboid and teres
major at the same time, and then the arm was depressed forcibly.
He adds that the rhomboid and teres major may be considered as
one muscle whose main function is to depress the arm, but he states
that its force is less than either of the two larger depressors of the
arm. Isolated action of the teres major, for some unexplained
reason, does not rotate the humerus with any considerable force.

Loss of the teres major does not interfere with depression of the
arm to nearly the same degree as loss of either the pectoralis major
or latissimus.

It is easy to observe the action of the teres major on the living
body in all movements involving forcible depression of the arm
and also when the body is suspended by the arms, either with the
hands grasping a fixed bar overhead or when the hands rest on two
parallel bars or desks with the arms at the sides. Since the trape-
zius is relaxed in these movements the rhomboid can be felt. Notice
also the complete relaxation of the deltoid in these exercises.

INFRASPINATUS AND TERES MINOR.

These two muscles, located on the back of the scapula, have
identical action, and hence will be studied together (Fig. .35).

Origin. — The outer surface of the scapula below the spine.

Insertion. — The posterior part of the greater tuberosity of the
humerus.

Structure. — Longitudinal converging fibers.

Action. — The point of insertion of these muscles being, as may
be seen in Fig. 35, directly opposite the center of the joint where
the articulating surfaces come in contact, it is evident that they
can have no power to raise or depress the arm, but, pulling hori-
zontally toward the median line of the back, will tend to rotate
the humerus outward. When the arms are elevated to shoulder
height, however, the line of pull is no longer at right angles to the
humerus but nearly in line with it, so that action of the infra-
spinatus and teres minor will in this position help to swing the arm
backward.

Isolated action of these muscles verifies the above conclusions
so fully that Duchenne suggests that they be renamed "outward

THE FUNDAMENTAL MOVEMENTS OF THE ARM 97

rotator of the humerus;" he states further that elevation of the
arm does not prevent the rotating action, which can extend through
90 degrees.

Persons who have lost the use of these muscles cannot use a
screw-driver efficiently and have great difficulty in writing, the
movement of the forearm across the page in writing being pro-
duced by the outward rotation of the humerus while the elbow is
flexed.

The outward rotators, while they are partly covered, can be
felt in action just below the posterior edge of the posterior deltoid
while the subject turns a screw-driver or a gimlet or twists the arm
as in wringing a wet cloth.

SUBSCAPULARS.

Named from its position on the anterior surface of the scapula,
next to the chest wall (Fig. 37).

Origin. — The whole inner surface of the scapula except a small
space near the joint.

Insertion. — The lesser tuberosity of the humerus.

Structure. — Converging fibers.

Action. — The position of the subscapularis, just opposite the two
muscles just studied, makes it appear to be an inward rotator of
the humerus; with the arm raised sideward, to pull the arm forward.
Experiments in electric stimulation, although not as conclusive as
in most cases, seem to verify these conclusions.

Action of the subscapularis in association with the outward
rotators would hold the head of the humerus firmly in the socket
and thus serve to prevent injury to the joint in many violent
movements of the arm; but the position of the subscapularis does
not allow of its being felt or seen in contraction and therefore it is
not certain that such action actually takes place.

THE FUNDAMENTAL MOVEMENTS OF THE ARM.

Having studied the muscles that move the arm on the trunk
and gained a certain familiarity with the individual action of each
and the conditions under which they act, we are now prepared to
study the mechanism of the various movements of the arm. It
seems best to take up first the fundamental movements — upward,
downward, forward, and backward — and then to study certain
gymnastic exercises which are but variations of the fundamental
movements.

We have already noticed that certain movements of the arm
involve motion not only in the shoulder-joint but also in the joints
7

98 MOVEMENTS OF THE SHOULDER-JOINT

of the shoulder girdle, and it will develop as we proceed that this
is true of practically all movements of the arm when they are
made with any considerable vigor. We will find that whenever
the arm is moved in either of its four cardinal directions or even
when it rotated on its long axis the shoulder-joint is itself moved
to the position most favorable; the glenoid fossa, by a gliding of
the scapula over the surface of the chest or a rotation upward or
downward, is brought so as to face in the right direction; and the
scapula is firmly anchored to the trunk so as to' make the glenoid
fossa a solid fulcrum on which the arm may swing as a lever, the
force being applied just where and when it is needed to keep the
axis in place during the movement.

Since the effect of gravitation is always directly downward it is
desirable to test the participation of the muscles by having a sub-
ject perform the exercises in different positions, such as standing,
lying with face downward and also with back downward, and
inclined positions that will affect the action and effect of the exer-
cise. Such a proceeding is helpful in deciding doubtful questions
of muscular action and questions regarding the relative merits of
exercises for special purposes.

ELEVATION OF THE ARM.

Normal elevation of the arm, starting from the position with the
arm hanging at the side of the thigh, takes place through 180
degrees, terminating in a position vertically upward; the arm can
be raised to this position in a plane directed forward or sideward
or any plane between these two; some young and flexible subjects
can carry the arm through an angle of a little more than 180 degrees
and in planes somewhat crosswise in front and somewhat to the
rear of the lateral plane, while other subjects are unable to raise
it as far as the vertical position. The resistance to elevation of the
arm is from two sources: gravitation and the tension of -ligaments
and antagonistic muscles. When weights are held in the hands or
the movement is made against the resistance of a pulley machine,
gravitation may prevent the subject from raising the arm to full
height; but the weight of the arm alone is a comparatively small
element in the case of those who are unable to put the arm straight
up. In the first place it is not especially the weaker individuals
who fail to make the complete movement; the weight of the arm
acts most effectively at the horizontal position and has less effect
above it, while the main difficulty these subjects experience in
raising the arm does not begin until it is considerably higher than
shoulder level; the difficulty is not removed by performing the
movement while lying on either the face or the back, which elimi-

ELEVATION OF THE ARM

nates the effect of weight of the arm. Continuous use of the arms
in lower planes without even occasional upward movements to
stretch ligaments and antagonistic muscles frequently modifies the
tissues so that they no longer permit the normal elevation. The
use of weights, such as dumb-bells and pulley machines, is frequently
employed to increase the resistance and thus hasten the develop-

Fig. 53. — Position of scapulae when arms are at sides.

ment of the muscles. The dumb-bells, acting only in the vertical
direction, have little effect on other muscles than those required
to raise the arms, while the pulley weights, with the three sets of
pulleys placed chest high, overhead, and on the floor, permit the
development of any muscle group of the body.

To raise the arm to vertical position requires movement in the
shoulder-joint and upward rotation of the scapula. It was formerly

100 MOVEMENTS OF THE SHOULDER-JOINT.

taught that this is accomplished by first making all possible move-
ment in the shoulder-joint and then rotating the scapula through
90 degrees, but as soon as students began observation of the living
body as a source of information it became evident that it is not
done in that way. While there is some variation in different sub-
jects one can easily convince himself that in the average young

Fig. 54. — Position of scapulae when arms have been raised through an angle of

45 degrees.

subject the scapula does not rotate more than 60 degrees and that
it does not rotate at all during the first part of the movement, nor
during the last part, but rather in the following manner, as the
accompanying figures illustrate.

In raising the arm sideward the humerus is first moved in the
shoulder-joint without any considerable movement of the scapula
through 45 degrees by the action of the middle deltoid and the

ELEVATION OF THE ARM 101

supraspinatus, while the entire trapezius, excepting the clavicular
fibers, contracts to prevent the scapula from being rotated down-
ward by the weight of the arm. During the next 90 degrees of
elevation both the scapula and humerus are moving, the lower ser-
ratus acting to swing the lower angle of the scapula forward. At
about the time the arm passes the horizontal the anterior fibers of

Fig. 55. — Position of scapulae when arms are raised through 90 degrees.

the deltoid begin to act to aid the middle part, and the upper trape-
zius also contracts. The upper 45 degrees of elevation takes place
in the shoulder- joint only. When the elevation is sideward the arm
must be rotated outward, preferably when near shoulder level, to
prevent the locking of the shoulder-joint by contact of the bones
at the top of the joint. When the arms are carried well to the rear
at the completion of the movement of elevation, and especially

Fig. 56

Fig. 57

ELEVATION OF THE ARM 103

when it is taken when lying on the face, the posterior deltoid acts
in some objects.

When the arm is raised forward there is this difference in the
mechanism of the movement : the middle deltoid is replaced during
the first 90 degrees of elevation by the anterior deltoid and the

Fig. 58
Figs. 56, 57 and 58. — Positions of scapulae in arm elevation above the horizontal.
Since the scapulae turn forward along the chest wall the full amount of rotation
cannot be shown in such a series of pictures.

upper half of the pectoralis major; above the horizontal there is
no difference. Observation of elevation diagonally between for-
ward and sideward shows that action of the deltoid is not neces-
sarily divided into the three divisions usually named, for portions
of the anterior and middle sections act in this case.

104 MOVEMENTS OF THE SHOULDER-JOINT

Many persons are unable to raise the arms above 135 degrees
without moving the head forward and elevating the chin, showing
strong action of the upper part of the trapezius and weakness or
lack of control of the muscles that hold the head erect. Some
writers say that the rhomboid acts in the later stages of arm eleva-
tion, but according to Sherrington's law of coordination it ought
to be fully relaxed, so as to permit complete upward rotation of
the scapula. In violent effort it may be brought into action through
an uncontrolled spread of nerve impulses, but it is very poor gym-
nastic training that encourages the use of muscles that hinder in
the work to be performed.

The pull of the deltoid is so nearly lengthwise of the humerus
that it tends to move the bone upward, lifting the head out of its
socket and pressing it against the under side of the acromion.
Contraction of the supraspinatus, which normally occurs along
with the deltoid, acts to keep the head of the humerus down in its
place; in this it is apt to be helped by the infraspinatus and the
subscapularis.

The movement of the lower angle of the scapula away from the
middle of the back as the arms are raised has been somewhat of a
puzzle to students of this subject. Although it has been shown
without question by Duchenne and others that the upper part of
the scapula is anchored by the trapezius and the lower angle pulled
forward in arm elevation by the serratus magnus, some recent
writers speak of "the tendency of the lower angle to follow the
arm, probably being pulled along after it by the teres major." To
avoid this error one must bear in mind that the scapula is the origin
of the pull that lifts the arm. The teres major is an antagonist of
the deltoid and must be relaxed to allow complete arm elevation.
If it should by any means be brought into action it would pull the
arm down with just as much force as it would pull the lower angle
forward. It may serve to move the lower angle forward when the
arm is raised up beside the head by another person, but that is not
normal arm elevation. When you raise your own arm up beside
the head the teres major is normally resting. Instead of the upward
rotation of the scapula being a result of the elevation of the humerus
it is really a cause of that elevation; the trapezius and serratus
rotate the scapula and rotate the whole upper limb along with it.

One question of interest remains, the location of the resistance
that necessitates the exertion required to raise the arms to vertical
position and that stops many persons before they arrive. There is
probably some resistance to the last stages of the movement in the
clavicular joints, and when the humerus strikes the acromion, if it
does, that and the pull of the supraspinatus will resist further
movement in the shoulder-joint; among the muscles, the rhomboid

DEPRESSION OF THE ARM

105

and pectoralis minor passively resist the extreme upward rotation
of the scapula, while the pectoralis major and latissimus resist the
elevation of the humerus. Since the difficulty of holding the arm
far enough back is so evident it would seem that the pectoral is
the greatest single factor in the resistance.

DEPRESSION OF THE ARM.

Normal depression of the arm, when there is no external resist-
ance, offers no such difficulties as elevation. Not only does gravi-
tation, when the trunk is erect, help instead of resist the movement,
but the arm is brought down against the side with no joints, liga-

Fig. 59.

-Depressors of the arm in action. P, pectoral; C, coracobrachial;
L, latissimus.

ments, or muscles impeding its way. It is the exact reverse of
elevation and all the planes possible in elevation are also possible
in depression.

The movements in the joints — depression of the humerus and
rotation downward of the scapula — appear to take place in the

106 MOVEMENTS OF THE SHOULDER-JOINT

reverse order of elevation, the movement of the scapula occupying
the middle half of the arm movement.

A convenient way to study the action of muscles in this move-
ment is to have the subject depress the arms while he holds the
handles of an overhead pulley machine. The movement can be
taken any desired speed and can be stopped at any level to notice
changes.

When the arm is depressed in the sideward plane against the
resistance of the pulley machine the pectoralis major, latissimus,
and teres major can be felt in action through the entire extent of
the movement; by placing the fingers on the ridges to front and
rear of the arm-pit these actions are easily detected. The scapula
does not rotate downward until the arm has lowered 45 degrees or
more, showing delayed action of the rhomboid and pectoralis minor
similar to what we have noticed of the lower serratus in elevation
of the arm. The pectoralis minor can be felt in contraction in the
middle phase of the movement. The rotation of the scapula,
although it starts late, is completed when the arm is about 45
degrees from the side, and the last stage of depression, like the
last stage of elevation, takes place in the shoulder-joint only. The
relative force of the pectoralis major and latissimus varies notice-
ably as the depression is made at different angles to the front and
rear of the lateral plane, the pectoral showing most tension when
the arm is forward and the latissimus when it is back. When the
movement is made in a plane as far to the rear as possible, the
posterior deltoid acts with the latissimus and teres major and the
pectoral is idle; the deltoid, however, stops acting when within
about 45 degrees of the side of the thigh. When it is in the forward
plane or internal to it the pectoral acts alone.

We have referred to a tendency in both elevation and depres-
sion of the arm for the head of the humerus to leave the socket,
because of the looseness of the ligaments and the direction of pull
of the muscles. There is a type of movements in this group where
this tendency is especially strong for another reason. In chopping
with an ax or striking with a heavy sledge, for example, the arm
and the tool is made to describe an arc so swiftly that centrifugal
force tends to pull the arm from the body, and when the tool
strikes to do its work the swing of the arm abruptly ceases and the
vigorous pull of the depressor muscles is brought to bear on the
joint in an oblique direction. To protect the joint from injury the
coracobrachialis and the long head of the triceps are useful here,
since they help somewhat in depressing the arm but exert most of
their force lengthwise of the humerus, holding it firmly up in place.

FLEXION OF THE SHOULDER-JOINT 107

EXTENSION OF THE SHOULDER-JOINT.

In most vertebrates the scapula is a long bone with its long axis
in line with its spine. The movements of the shoulder- joint in
man are named according to the general rule and therefore the
sideward horizontal position, when the humerus is in line with the
principal axis of the scapula, is called the position of extension, and
movements of the arm backward in the horizontal plane are called
movements of extension of the shoulder-joint. Swinging the arm
horizontally backward behind the lateral plane is called over-
extension. Overextension is brought to a stop 20 to 30 degrees
back of the lateral plane by the tension of the coracohumeral liga-
ment and the pectoralis major muscle acting on the humerus, and
in some subjects also by tension of the upper serratus and pectoralis
minor, acting on the scapula.

As the arm is carried horizontally backward against resistance to
the positions of extension and overextension from a starting-point
toward the front, the middle and posterior portions of the deltoid
are seen to act in swinging the humerus, aided by the infraspinatus
and teres minor, while the lower three-fourths of the trapezius
adducts the scapula. If the arm is allowed to fall much below
shoulder level the rhomboid, teres major, and latissimus come into
action, but at or above the horizontal they do not act.

FLEXION OF THE SHOULDER-JOINT.

Flexion of the shoulder-joint, by which is meant a forward
movement in the horizontal plane, is limited in front by contact
of the arm with the front of the chest and in some subjects by ten-
sion of" opposing muscles, principally the trapezius, rhomboid, and
infraspinatus.

When the arms are carried horizontally forward against an
external resistance, such as that of a pulley weight, the scapula?
can be seen moving forward, by action of the serratus and pectoralis
minor, while the anterior deltoid and both parts of the pectoralis
major pull the humerus forward. Notice how the clavicles keep
the plane of the scapula well in line with the humerus through the
movement, so that the glenoid fossa is at each stage turned in the
best direction to support the humerus; notice how the scapula
rotates to keep this relation when the flexion is made a little above
or below the horizontal plane, controlled by action of the lower
serratus and rhomboid.

The uniform manner in which all subjects perform the four funda-
mental movements of the arm — elevation, depression, flexion, and
extension, gives us reason to believe they are inherited coordina-

108 MOVEMENTS OF THE SHOULDER-JOINT

tions, like walking, running, etc., developed by nature as the race
has developed, so as to get the work done in the most economical
and efficient way. Such coordinations are not easily changed, even
if they could be improved, and it would seem wise for teachers of
gymnastics to use exercises that bring in these normal movements
rather than to try to invent new ones on a different plan.

GYMNASTIC MOVEMENTS.

A gymnastic movement, as the term is now understood, is a
movement taken in imitation of a pattern or model shown or
described, and therefore is always predetermined and defined, as
to its starting position, its course, its speed, and its terminal posi-
tion. Gymnastic movements are devised to accomplish some pur-
pose in the mind of the inventor, which purpose may be to develop
or improve the tone of some muscle group, stretch some muscle or
ligament, influence the circulation of lymph or blood, acquire skill
or "form" in some exercise to be used in competition, form certain
habits of movement or posture, etc.

The Swedish system of gymnastics developed at the Royal Gym-
nastic Institute in Stockholm in accordance with principles stated
by Ling, the founder of the system, aims to secure, by a few care-
fully selected exercises, definite effects on the vital organs of the
body. The exercises are all chosen and defined by the authors of
the system and are therefore practically identical wherever used.
Much attention is paid to correction of faulty postures and com-
paratively little apparatus is used.

The German system includes many more exercises and the exact
details of the definition of these exercises is left more to the individual
instructor, so that no particular exercise stands out as the product
of the system. Devised originally to promote public interest in
bodily exercise, the German system is varied to meet conditions
and local needs. It gives less attention than the Swedish to cor-
rective exercises and uses apparatus more extensively. Dumb-bells,
wands, Indian clubs, and stationary apparatus, such as parallel and
horizontal bars, vaulting horse, swinging rings, etc., are examples of
apparatus used in this system.

A form of apparatus of special interest here is the pulley weight
invented by Dr. D. A. Sargent and found in every well-equipped
gymnasium. Noticing that the weights used in German gymnas-
tics, such as dumb-bells, wands, etc., are of use to develop the
elevators of the arms almost exclusively, since their weight always
acts vertically downward, he tried to devise an apparatus by
which one could give various degrees of resistance to the action of
depressors, flexors, and extensors as well. The final result is a

GYMNASTIC MOVEMENTS 109

combination of a set of adjustable weights with three sets of pul-
leys, placed shoulder high, overhead, and on the floor, meeting the
need admirably.

Raising Arms Sideward (Swedish). — This is taken with palms down
and the arms held a little behind the lateral plane, terminating at
the horizontal with the arms carried as far to the rear as possible.
The object here is improved posture of the chest, gained through
adduction of the scapulae and some elevation of the ribs. The

Fig. 60. — Arms sideward, as taken in Swedish gymnastics.

scapula is drawn back by the trapezius and the arm held up and
drawn back by the supraspinatus, middle and posterior deltoid,
assisted somewhat by the infraspinatus and teres minor; this puts
a tension on the two pectorals and thus lifts somewhat on the ribs
on the front of the chest; Taken in this way this is a perfectly
normal extension of the shoulder-joint, but writers on the theory
of Swedish gymnastics are inclined to urge the use of the rhomboid
and latissimus, "to flatten the back and help adduct the scapulse."

110 MOVEMENTS OF THE SHOULDER-JOINT

They infer that the vertebral border of the scapula should be parallel
to the median line, apparently forgetting that normal elevation of
the arm to horizontal requires upward rotation of the scapula and
contraction of the lower serratus; action of the rhomboid and
serratus together will do nothing but lift the scapula vertically —
something they want the latissimus brought in to prevent. The
normal rotation of the scapula is also needed to give the tension on
the pectoralis minor that is specially desired, while the action of
the latissimus and rhomboid would prevent it. For these reasons
the normal movement of shoulder extension seems best adapted
to secure the results desired; the added action of the rhomboid
and latissimus occurs in the awkward and less effective attempt of
a beginner who tries with all his might and thus by uncontrolled
spread of nerve impulses stimulates muscles that do more harm
than good.

Raising Arms Sideward (German). — This is normal elevation of
the arm in the lateral plane with no effort at overextension and
with palm turned in either direction to suit the purpose of the
instructor. It is often but not always performed with weights in
the hands.

Raising Arms Sideward (Sargent) .—This is the same movement
as the last with palms down with the resistance of the weight
directed by a pulley at the floor. It permits normal elevation with
resistance conveniently adjustable to suit the strength of the
individual.

Outward Rotation of the Palm (Swedish), with arms raised side-
wise or combined with it is difficult because the infraspinatus and
teres minor, the chief outward rotators of the humerus, are in a
position to aid in the overextension rather than in the rotation,
while the inward rotators — pectoral, latissimus, and teres major —
have increased tension because of the position of the arm. The
rotation is easier in the German form of the exercise because the
outward rotators are not employed to hold the arm back.

Raising Arms Forward (Swedish). — This is taken with palms
toward each other and parallel, stopping at the horizontal with
effort to adduct the scapula as far as possible (Fig. 61), according
to some authorities, while others say nothing on this point. One
prominent author says that all "displacements" of the shoulder
girdle should be reduced to a minimum as they tend toward " vicious
habits" of movement, but it seems questionable whether normal,
economic, and graceful associations of the arm and shoulder girdle
in movements like this, which have been fixed in the nervous
system by ages of habitual coordination, should be stigmatized as
"vicious habits of movement" because they do not aid in chest
expansion. If all arm movements are useless for gymnastic pur-

GYMNASTIC MOVEMENTS

111

poses unless they produce chest expansion by powerful adduction
of the scapula, it would seem wiser to restrict our choice to arm
movements that naturally do this rather than to disrupt normal
and useful reflexes in order to secure complete adduction of the
scapula when. the normal movement does not permit it. For prac-
tical purposes of life a forward elevation of the arm with com-
pletely adducted scapula is useless, since it produces such extreme
flexion of the shoulder-joint as to make pushing, striking, or lifting

Fig. 61. — Arm raising forward. (Swedish.)

dangerous to the structure of the joint; if one should strike a blow
forward vigorously in this position (Fig. 61) the head of the humerus
would probably go straight back through the posterior side of the
capsule of the joint. The use of the exercise, taken in the normal
way, is justified even for posture, because it shifts the balance of
the trunk and leads the untrained pupil to tip backward at the
waist line until he is trained to maintain normal posture under
changing conditions.

112 MOVEMENTS OF THE SHOULDER-JOINT

Raising Arms Forward (German, Sargent). — These are normal
movements involving no new problems except that of balance of
the trunk, which will be discussed in a later chapter.

Arm Parting (Swedish) and Swinging Arms Sideward (German,
Sargent). — These are all taken from the previous exercise as a
starting-point and are all normal extensions of the shoulder-joint,
excepting that the Swedish movement is continued as far as pos-
sible into overextension and has palms down.

Fig. 62. — The normal forward position of the arm as used in pushing and
striking, the scapula being considerably abducted.

Raising Arms Sideward-upward and Forward-upward. — These are
normal elevations of the arms to vertical position, taken in the
German and Sargent systems for muscular development and in
the Swedish system for chest expansion. The upward rotation of
the scapula lifts on the pectoralis minor and through it lifts on the
ribs, while the elevation of the humerus acts in the same way on
the pectoralis major and those fibers of the latissimus that arise
from the ribs, so that the movement may well aid in chest expan-
sion. Many writers mention the serratus as an elevator of the ribs,

GYMNASTIC MOVEMENTS

113

but it is difficult to see how it can do so directly, since it pulls down
on quite as many ribs as it pulls up; it seems more likely that it
acts only indirectly by rotating the scapula and thus works through
the pectorals. Exponents of the Swedish system insist here, as in
most arm movements, on the use of the rhomboid and the latis-
simus "to aid the trapezius," failing to consider that these muscles
are direct antagonists of arm elevation and
therefore antagonists of the trapezius when-
ever arm elevation is involved.

When we recall that the utmost traction on
the ribs, which the Swedes desire, requires
complete elevation of the arm, and that this
is impossible without complete upward rota-
tion of the scapula, which action of the rhom-
boid prevents, it is hard to see how the intro-
duction of this antagonist can improve the
result. The argument for use of the latissimus
is nearly as weak; it pulls down on the arm
much more than it pulls back, when the arm
is up to vertical, so how can its action put
more tension on the pectorals to lift the ribs?
If the muscles used in normal elevation of the
arm are weak or the opposing muscles are
short, it will be hard enough to put the arms
up to vertical without action of antagonists;
if it is so easy for anyone to put the arm up
to vertical that he needs more work, it would
seem wiser to add to the resistance by a dumb-
bell or a pulley weight rather than to upset
the normal coordination by the use of muscles
that do not normally take part.

Raising Arms Backward (Swedish) . — This be-
gins with arms at sides of thighs and the arms
are carried backward as far as possible. This
is a combination of extension and depression,
using all the posterior depressors and including the posterior deltoid.
The same movement is taken in the Sargent system by standing fac-
ing the chest weight and, starting from forward horizontal, swing-
ing the arms down past the thighs. The effect is almost the same
in striking dumb-bells behind the hips (German), which may start
from overhead, side or front horizontal, or any other convenient
position.

An interesting relation between the use of pulley weights and
some forms of stationary apparatus appears when we consider
what happens if the weight is increased. If the weight attached to

Fig. 63.— Arms
upward.

114 MOVEMENTS OF THE SHOULDER-JOINT

an overhead pulley is increased indefinitely the point is eventually
reached, if the subject is strong enough to do the work, when this
weight is greater than that of his body; when this time arrives, in
place of the weight going up he will go up as the result of the action
of his depressor muscles, changing the apparatus at once to the
stationary type, like the parallel bars or the suspended rings. In a
similar way, if we increase the weights of the chest pulley while
the subject is swinging arms down past the thighs, when the weight
equals his own we may replace the pulley machine by a pair of
suspended rings or a horizontal bar and he will, with the same move-
ment of the arms, lift his body and swing his feet above his head.
This leads to the conclusion that work on stationary apparatus,
such as bars, rings, and the like, is apt to be in the main for the
depressors of the arm, just as work with dumb-bells is for the
elevators.

QUESTIONS AND EXERCISES.

1. Pick out a humerus from the bones of a dismembered skeleton; point out and
name its two extremities, its two tuberosities, its two condyles, its bicipital groove;
tell whether it is right or left humerus.

2. Write in a column the names of the six movements of the shoulder-joint; in
a parallel column 4 inches away write the names of the nine muscles acting on this
joint; by lines connecting movement with muscle indicate the actions of each
muscle.

3. Explain why those who cannot raise arms up to vertical usually complete the
exercise with arms in front of the vertical; explain why the action of the rhomboid
will add to the difficulty.

4. Demonstrate with a pulley machine exercises for developing each of the nine
muscles acting on the shoulder-joint.

5. Explain why dumb-bell exercises develop the trapezius more than the rhom-
boid; the anterior more than the posterior deltoid.

6. Explain why exercises on bars and rings develop the latissimus and the rhom-
boid so much more than the deltoid and trapezius.

7. By use of a ruler or tape find the length of the power arms in case of each of
the nine shoulder muscles.

8. With a loose scapula and humerus demonstrate how elevation of the humerus
is limited in the shoulder-joint; how the rotation of the humerus permits further
movement; how elevation can be greater at the front than at the rear.

9. By mears of an inelastic cord attached to the mounted skeleton, find the extent
of contraction of each of the nine muscles and thus find the length of their muscular
fibers.

10. If the deltoid pulls with a force of 400 pounds and the supraspinatus with a
force of 200 pounds, how much will they together lift at the hand when the arm is
horizontal? Find distances and angles of pull by reference to the skeleton.

CHAPTER VI.
MOVEMENTS OF ELBOW AND FOREARM.

The arm has a hinge joint at the elbow and a rotary union of
radius and ulna in the forearm.

The elbow is a typical hinge joint, the humerus articulating
closely with the ulna and slightly with the radius. The movements
are flexion and extension, taking place through an angle varying
in different subjects from 120 to 150 degrees. Extension is limited
by contact of the olecranon process of the ulna against the posterior

Fig. 64. — The elbow-joint, outer side. (Gerrish.)

side of the humerus; flexion is limited by contact of the muscles
on the front of the arm. Some individuals can overextend the arm
at the elbow while others cannot fully extend it, the difference
being due mainly to occupation, habitual position of the joint and
variation in the laxness of ligaments. The capsule of the joint is
reinforced by strong bands of connective tissue on the outer and
inner sides.

The radio-ulnar union is a double pivot joint, the radius rota-
ting in a ligamentous ring at the elbow and the lower ends of the
two bones describing semicircles around each other at the wrist.
The ulna cannot rotate at the elbow and the radius cannot rotate

116

MOVEMENTS OF ELBOW AND FOREARM

at the wrist, yet by means of the peculiar manner of union between
the two the hand can turn through nearly 180 degrees. This,
together with the 90 degrees of rotation possible in the shoulder-
joint, makes it possible to turn the hand through almost 270 degrees
when the elbow is extended. The position with palm upward is

Fig. 65. — Muscles on the back of shoulder and arm. (Gerrish.)

called the supine position, and the rotation of the forearm inward
and upward to this position is called supination; the position with
palm downward is called the prone position of the arm, and the
rotary movement to this position is called pronation.

There are five muscles acting on the elbow-joint; two of these

TRICEPS

117

also have some action on the shoulder-joint and two act also on
the radio-ulnar union. Two muscles act on the radio-ulnar union
only, giving the following list :

^ow ifrsr

Radio- [ Supination

■ulnar <

Union [Pronation

Triceps

Biceps

Brachialis

Brachioradialis

Pronator teres

Pronator quadratus

Supinator

TRICEPS.

The triceps is on the posterior side of the upper arm, and, as its
name implies, has three separate places of origin (Fig. 65).

Origin. — (1) The middle or long head, from the scapula, just
below the shoulder-joint; (2) the external head, from a space half
an inch wide on the back of the humerus, extending from the
middle of the shaft up to the greater tuberosity; (3) the internal
head, from the lower part of the back of the humerus, over a wide
space extending nearly two-thirds of the length of the bone.

Insertion.— The end of the olecranon process of the ulna.

Structure.— The long head has a short tendon of origin; the fibers
of the other two parts arise directly from the humerus. The ten-
don of insertion is flat, and as it leaves the ulna it broadens into a
thin sheet that extends far up the external surface of the muscle
and the muscular fibers attach obliquely to its deeper surface.
The long head passes up between the teres major, lying in front,
and the teres minor, behind it.

Action.— The olecranon process of the ulna extends past the
elbow-joint and the triceps is inserted into the end of it, making
of the ulna a lever of the first class. Since the triceps pulls up on
the olecranon it will evidently move the main part of the lever
down and thus extend the elbow-joint. The leverage is short,
favoring speed rather than power; the angle of pull is nearly 90
degrees through a large part of its movement, the tendon passing
over the lower end of the humerus as a pulley; the great number
of short fibers in its structure, together with its large angle of pull,
gives the muscle great power as well as speed. The origin of the
middle head on the scapula enables that part to act on the shoulder-
joint as well as the elbow; a rubber band looped around the olec-
ranon and held at the point of origin shows plainly that its pull
is chiefly lengthwise of the humerus, lifting its head up into the
glenoid cavity. If the humerus is lifted the tension on the rubber
band is increased, showing that it is able to aid in depressing the
arm, but its angle of pull is here very small.

118 MOVEMENTS OF ELBOW AND FOREARM

Loss of the triceps destroys a person's ability to extend the elbow
forcibly, but does not disable him for light tasks, since the weight
of the forearm will extend the elbow when there is no resistance,
making it possible to use the hands in any position when the move-
ment requires little force.

Stimulation of the different parts of the triceps causes extension
of the elbow with great speed and power. Duchenne states that

Fig. 66. — The triceps in action. 0, outer portion; M, middle portion; /, inner

portion.

the long head has much less power to extend the elbow than the
other two parts, but this is no doubt due largely to the fact that he
used electric stimulus when the subject was standing at ease, the
scapula and humerus not being held in place firmly as they are in
normal coordinated action. The action of the long head to depress
the humerus and lift the humerus lengthwise is plainly shown in
Duchenne's experiments.

The triceps can be seen and felt in vigorous action in all move-

BICEPS 119

ments involving forcible extension of the elbow; its action is promi-
nent in such exercises as boxing, putting the shot, driving nails,
thrusting dumb-bells, pushing a lawn mower, chopping with an
ax, shovelling, etc.

BICEPS.

A prominent muscle on the front side of the upper arm with two
separate places of origin (Fig. 50).

Origin.— (1) The outer or long head, from the scapula at the
top of the glenoid fossa, the tendon passing over the head of the
humerus and blending with the capsular ligament of the shoulder-
joint; (2) the inner or short head from the coracoid.

Insertion. — The bicipital tuberosity of the radius.

Structure. — The tendon of the long head is long and slender and
lies in the bicipital groove of the humerus, becoming muscular at
the lower end of the groove. The tendon of the inner head is shorter,
the muscular fibers of the two parts being of equal length. The
tendon of insertion is flattened as it joins the muscle and passes up
as a septum between the two parts and receives the fibers in a
penniform manner from both sides.

Action. — The biceps is in a position to act on three joints: shoul-
der, elbow, and forearm. Tension on the long head will surely
help to hold the head of the humerus in the socket and the inner
head will act with it to lift the humerus lengthwise. Both parts
act to flex the elbow, the power arm being somewhat over an inch
in length and the angle variable from 15 to 20 degrees in the posi-
tion of complete extension up to 90 degrees when the elbow is
flexed to about a right angle and diminishing again as flexion con-
tinues. When the hand is placed in extreme pronation the bicipital
tuberosity of the radius is turned inward and downward, wrapping
the tendon of the biceps more than half-way around the bone;
contraction of the muscle will evidently tend to unwrap it and thus
supinate the hand. Both the flexing and supinating actions of the
biceps will take place to best mechanical advantage when the arm
is half flexed.

Isolated action of the biceps flexes the elbow, supinates the hand
and lifts the humerus up into the shoulder-joint, without raising
the arm.

Loss of the biceps does not make one unable to flex the elbow,
since there are other muscles able to perform this movement;
those who have the use of the other flexors but lack the biceps can
do light work readily, but when they try to lift heavy objects the
weight pulls the head of the humerus down out of its socket, caus-
ing pain and quick fatigue. When all the flexors are lost the use
of the arm is practically abolished, as the subject cannot lift the

120

MOVEMENTS OF ELBOW AND FOREARM

hand to the face nor touch the body with the hand above the
middle of the thigh; this makes it impossible for him to dress or
feed himself.

The biceps can be observed in action in all movements involving
forcible flexion of the elbow, such as lifting, rowing, climbing, and

STYLOID
PROCESS

POSTERIOR.
BORDER

POSTERIOR
BORDER

STYLOID
PROCESS

Fig. 67 Fig. 68

Figs. 67 and 68. — The radius and ulna. (Gerrish.)

the like; in all forcible supination, as in turning a screw-driver to
turn a screw in with right hand or out with left; when the arm
is raised sideward it seems to contract during a horizontal swing
of the arm forward, but this may be done to protect the elbow
against injury from overextension, which the movement tends to
produce.

BICEPS

121

When the biceps is stimulated by electricity it flexes the elbow
and supinates the forearm at the same time, and the question arises,
How does one perform these two movements separately and use
the biceps in both? Anyone can easily demonstrate on his own arm
that he can flex the elbow without difficulty with the forearm in
any position from extreme pronation to extreme supination, and
can supinate the forearm while J;he elbow is in any position between
complete flexion and complete extension, the biceps acting in all

Fig. 69. — The biceps in action.

cases. Evidently the will can do nothing directly to cause one of
the two movements separately, for it can do no more than stimu-
late the muscle to action.

The reader can find a clue to the problem by making the follow-
ing easy test : stand in front of the person who acts as subject and
facing him, with your left hand grasping his upper arm loosely with
the finger-tips resting on the triceps and the thumb on the biceps,

122 MOVEMENTS OF ELBOW AND FOREARM

so as to be able to detect any contraction of either; now have him
supinate the forearm strongly while with your right hand you
grasp his hand to resist the movement he makes, and notice how
both his biceps and triceps contract at the same time. Evidently
the biceps is acting to supinate the forearm, but why is the triceps
working? Beevor, who first explained the matter, says that the
triceps acts to prevent the elbow from being flexed by the action
of the biceps, and that this is the way such actions are separated in
all cases of this kind. For example, when the latissimus, pectoralis
major and teres major act to depress the arm they also tend to
rotate it inward, for they all attach to the humerus in a way to
produce this combined action; to prevent this rotation, which is
not wanted in driving nails with a hammer, the infraspinatus and
teres minor contract — not to help directly in depressing the arm,
as some observers have concluded, but to prevent the rotary action
produced by the depressors.

All this has a bearing on the interesting problem of the use of a
screw-driver. When any considerable force is needed to turn the
screw it is also necessary, as all know who have used this tool, to
push hard to keep the tool in the slot in the top of the screw. How
can we turn the screw, which requires action of the biceps, and at
the same time push, which requires action of the triceps? Exami-
nation of the arm while the work is being done will convince any-
one that both muscles are in action at the same time. Every pound
of pull of the biceps acts on the elbow-joint to neutralize the pull
of the triceps, and the biceps has much the better leverage. How
can the triceps extend the elbow with any force under these condi-
tions? The only explanation seems to be that the triceps, because
of its structure, is stronger than the biceps, or that the biceps is
inhibited from its full contraction when we try to push with greatest
force. The force of the push must be the amount by which the
action of the triceps exceeds that of the biceps, and the stronger
we push the less force can be used to turn the screw. It is also
interesting to notice that when this tool is used with the elbow
bent to a right angle only the muscles we have just mentioned take
part in turning it; but when the elbow is fully or almost extended
the infraspinatus and teres minor act too, since in this position
supination and outward rotation are combined.

BRACHIORADIALIS.

This muscle was named "the long supinator" by the ancient
anatomists, but its action has been found to be different and its
name has therefore been changed. "Brachium" is the Latin for

PRONATOR TERES 123

the upper arm, so that the present name indicates its attachment
to the radius and humerus. It is situated on the outer border of
the forearm and gives rise to the rounded contour from the elbow
to the base of the thumb (Fig. 70).

Origin. — The upper two-thirds of the external condyloid ridge of
the humerus.

Insertion. — The external surface of the radius at its lower end.

Structure. — Arising directly from the humerus, the fibers join the
lower tendon in a penniform manner.

Action. — The position of the brachioradialis indicates it as a
flexor of the elbow; its leverage is long but its angle of pull very
small; computation shows that when both are taken into account
it has better mechanical advantage than the biceps. Its location
suggests that it will turn the forearm into a position midway between
pronation and supination.

Isolated action of the brachioradialis flexes the elbow with great
force and either pronates or supinates, according to the position of
the hand when it contracts.

Study of the normal action of this muscle, which is easily made,
shows that it takes part in flexion of the elbow, its fibers lifting
the skin near the joint as soon as the slightest flexion takes place.
When it is observed during voluntary pronation and supination it
is seen to lie idle in both cases, but if any movement of flexion
occurs with the rotation it at once springs into action.

BRACHIALIS.

Literally translated, "muscle of the upper arm." It is located
between the biceps and the humerus near the elbow (Fig. 50).

Origin. — Anterior surface of the humerus for its lower half.

Insertion. — Anterior surface of the ulna near the elbow.

Structure. — The tendon of insertion flattens into a thin sheet and
the muscular fibers, arising from the humerus, are attached obliquely
to its deeper surface.

Action. — Simple flexion of the elbow is indicated by conditions
of action and verified by electric stimulation. It can be felt during
strong flexion of the elbow, swelling out laterally between the biceps
and the bone; its leverage fits it for speed rather than power.

PRONATOR TERES.

A small spindle-shaped muscle lying obliquely across the elbow
in front and partly covered by the brachioradialis (Fig. 70).

124

MOVEMENTS OF ELBOW AND FOREARM

Origin. — Front side of the internal condyle of the humerus.
Insertion.— Outer surface of the radius near its middle.

Structure. — Fibers arising from short
tendons join the tendon of insertion
obliquely, the latter lying beneath the
muscle for half its length.

Action. — A rubber band looped
around the radius at its middle so as
to pull from the outer side, with its
free end held with some tension at the
inner condyle, readily produces pro-
nation, followed by a slight amount
of flexion. Isolated action gives the
same result.

The pronator teres can be seen and
felt in contraction without much diffi-
culty in favorable subjects. In pure
flexion it acts with the biceps, its pro-
nating action neutralizing some of the
supinating action of the larger muscle.
In pure pronation against a resistance
the triceps can be felt in mild Contrac-
tion to neutralize the flexing action of
the pronator teres, just as it acts with
the biceps in supination, but much less
vigorously.

PRONATOR QUADRATUS.

A thin square sheet of parallel fibers
lying deep on the front of the forearm
near the wrist (Fig. 71).

Origin. — Lower fourth of the front
side of the ulna.

Insertion. — Lower fourth of the front
side of the radius.

Structure. — Parallel fibers attached
directly to the bones.

Action. — Pronation, as judged by its
Fig. 7o.-sUperficiai muscles of position. Isolated and normal action

the front of the forearm. (Gerrish.) not tested.

SUPINATOR.

Formerly called "the supinator brevis" to distinguish it from
the so-called "supinator longus" which has been renamed, making

SUPINATOR

125

Fig. 71. — Deep- muscles near the wrist. (Gerrish.)

EXTERNAL
CONDYLE

OLECRA-
NON

ULNA RADIUS

Fig. 72. — The supinator. (Gerrish.)

126 MOVEMENTS OF ELBOW AND FOREARM

the adjective unnecessary. The muscle is a small one situated on
the back of the arm just below the elbow.

Origin. — External condyle of the humerus, neighboring part of
the ulna, ligaments between.

Insertion. — Outer surface of the upper third of the radius.

Structure.— Mostly parallel fibers.

Action. — Supination, as shown by its position and isolated action.

Fig. 73. — Pushing forward with both arms.

FUNDAMENTAL MOVEMENTS.

The upper limb as a whole has at least four fundamental move-
ments definitely fixed in the nervous system: pulling, pushing,
striking, and throwing.

Pulling. — Pulling is a combination of elbow flexion and arm
depression, illustrated well by grasping the handles of the chest
pulleys with arms at front horizontal and drawing them to the chest;

FUNDAMENTAL MOVEMENTS 127

the same is true when handles of overhead pulleys are pulled down
to same place. The elbows are completely flexed and the humerus
depressed and carried far backward.

Pushing. — Pushing, which is most readily done forward, is a com-
bination of extension of the elbow with elevation of the arm, pro-
duced by action of the triceps, anterior deltoid and upper pectoralis
major, aided by the serratus and pectoralis minor to bring the
scapula forward.

Striking. — Striking forward, as in boxing (see Fig. 62), involves
the same movement of the arm as pushing and uses the same muscles,
but the manner of doing it is very different. In pushing one places
his hand on the object to be pushed before the push is made, while
in boxing the fist is given the utmost speed by the arm movement
before the object is reached.

Fig. 74. — The starting position for throwing.

A turn of the body can increase the speed of the blow and for
that reason the boxer can do best by striking with one hand at a
time.

When striking is done with a weapon or tool the blow may be
made forward as in boxing, illustrated by a thrust with a sword,
but more often is given by a downward swing of the arm as in
driving nails with a hammer, using the arm depressors along with
the triceps. This gains the advantage of the weight of the arm and
tool and permits momentum to be gained by the wide swing.

Throwing. — Throwing, in its simplest form, as seen in throwing
done by small children and by older people who have not had m'uch
practice, consists of a forward swing of the straight arm. The hand
holding the object to be thrown is raised high overhead and then
swung forward by the action of the arm depressors. The hand

128

MOVEMENTS OF ELBOW AND FOREARM

describes the arc of a circle about the shoulder-joint as a center,
and when the object is released by relaxing the grasp it goes on in
the direction it was travelling at that instant, following a line tangent
to the circle. A ball can be thrown with considerable force in this
way, but it is not easy to aim accurately because the hand, moving
in a circular path, changes its direction at every moment and the
object must be released at the exact instant or it goes wide of the
mark.

In the more complex coordination used by ball-players who have
had much practice the circular movement of the hand is changed
to almost a straight line. This makes it easier to hit the mark, for
if the projectile is moving in a straight line toward any point it
matters little when it is released. To change the motion from a
curve to a straight path the arm is moved far back instead of

Fig. 75. — The finish in throwing.

upward, and as the humerus swings forward by action of the pec-
toral and serratus the elbow is flexed and then extended to just
the right extent. Beginners who try this plan make a zigzag at
first, but with practice a straight line can be made, in the air by
the moving hand.

Accurate throwing depends on making a nearly straight line and
making it in exactly the right direction. Speed of throw depends
upon how long the hand keeps in contact with the ball and keeps
increasing its speed; the farther back one starts and the farther
forward the ball is released the more speed one can give it.

Throwers use the triceps, posterior deltoid, lower serratus and
trapezius mildly in preparing to throw. In the throw they use the
biceps group followed quickly by the triceps, and at the same time
the pectoralis major, serratus and pectoralis minor contract with
all the speed and power they possess.

GYMNASTIC MOVEMENTS

129

GYMNASTIC MOVEMENTS.

Shoulders Firm (Swedish) . — This is an exercise intended to adduct
the scapula and expand the chest. Starting with arms hanging at
the sides, the elbows are flexed and the hands brought up by the
shoulders and carried to the rear as far as possible; at the same
time the elbows are held as close to the sides as possible (Fig. 76).
The effort to put the hands far back calls the posterior deltoid into
action along with the infraspinatus and teres minor, while the

Fig. 76. — The Swedish exercise "shoulders firm," or "arms bead." The position
of the right arm illustrates a common fault; the hand is not held back far enough to
give complete adduction of the scapula.

effort to keep the elbows down brings in the rhomboid, latissimus,
and teres major. The outward rotation wraps the tendon of the
latissimus around the humerus and thus increases its pull on the
arm and shoulder, while the inner head of the biceps tends to resist
the rotation outward. The backward movement of the arm and
shoulder pulls on the two pectoral muscles and thus lifts the ribs.
Arm Stretchings (Swedish) or Thrustings (German). — These are
vigorous extensions of the elbows starting from "neck firm,"
"shoulders firm," or some other position in which the elbows are
flexed., The arms finish in one or another of the positions taken in
9

130 MOVEMENTS OF ELBOW AND FOREARM

arm raising — forward, sideward, upward, downward, or backward.
In the first three of these the action of the triceps is combined with
arm elevation; in the latter two it is combined with vigorous arm
depression. Besides the muscular training of the extension move-
ments these exercises are useful because they afford variation in a
continued practice of "neck firm" and "shoulders firm," two of
the best posture exercises.

Several pulley exercises (Sargent) belong here. Grasping handles
of overhead pulleys and moving them downward in parallel straight
lines until the arms are down beside thighs, combines work for the
flexors of elbow and depressors of arm until elbows reach the sides,
when extension of elbow takes the place of flexion. Standing facing
the chest pulleys and moving handles to chest uses elbow flexors
and arm depressors; standing with back to same pulleys and with
ropes just over or under arms move them forward to horizontal
from the chest brings in extensors of elbow with elevators of arm.
Grasping handles of floor pulleys beside thighs and moving them
in parallel straight lines upward to vertical position illustrates
typical lifting, an exercise so important as to need special notice.

If one wishes to lift a heavy dumb-bell in the easiest way he
keeps as near a vertical line as possible, since this makes the short-
est possible weight-arms to work against. The complete move-
ment of lifting any such weight up to vertical position includes
three stages: (1) a vertical lift from the position beside the thigh
to the level of the armpit; (2) a short semicircular movement from
the point just below the shoulder-joint to the point above and in
front of it; (3) vertical movement until the arm is extended upward.
Stage (1) is performed by the flexors of the elbow, with the acromion
held up by the levator and second part of the trapezius; the elbow
projects far to the rear, due to the weight, which will hang verti-
cally below the shoulder-joint if free to do so. When this point
is reached the flexors hold the elbow completely flexed while the
elevators of the arm carry the humerus forward nearly to the hori-
zontal, which moves the weight through the curved path of stage
(2). From this point on to vertical position upward the extensors
of elbow act with the elevators of the arm to complete the move-
ment. The question as to which stage of the lift is most difficult
will be answered differently, depending on which muscles are most
fully developed — flexors, extensors, or elevators. This analysis of
the movement may often be seen by observing labor of various
kinds, such as loading railroad iron on cars, loading crates into a
high wagon, loading trunks on a train, etc.

Hanging by the Hands. — When one grasps something above his
head and hangs vertically downward, the flexors of the hands are
the only muscles that must act, because the weight of the body

GYMNASTIC MOVEMENTS

131

holds the arms and body in the erect position that would under ordi-
nary circumstances require some muscular action. Two muscles,
the pectoralis major and latissimus, join the arm to the trunk; the
weight of the body is partly borne by these and partly by the muscles
joining the humerus to the scapula and those that join the scapula
to the trunk. Of all these the two pectorals and the lower fibers

Fig. 77. — Chinning the bar.

Fig. 78. — Cross rest on parallel bars.

of the latissimus attach to the ribs, and since most of the weight
of parts below is joined to the spinal column rather than to the ribs,
hanging by the hands is apt to produce some chest expansion and
hence has value as a posture exercise. If the subject, while hang-
ing by his hands, can adduct his scapulae by the use of any or all
the muscles on the back of the shoulders, more tension will be
thrown on the pectorals and the ribs will be lifted still more.

132 MOVEMENTS OF ELBOW AND FOREARM

Chinning the Bar. — When a person who is hanging by his hands
tries to lift his body with his arms he brings into play the flexors
of the elbow and depressors of the humerus. The exercise, com-
monly called "chinning the bar," is a popular test of the muscles,
a boy of fourteen who can lift himself in this way until he can rest
his chin on the bar six times in succession being considered fairly
strong. Besides developing the arms the exercise is considered
good for the posture of the chest if the subject is able to do it with-
out bowing his back and lifting his legs, because the action of the
pectorals on the ribs is stronger than in simply hanging by the
hands and will lift them farther unless other muscles that pull
down on the ribs from below prevent it; for this reason the exercise
is not devised as a corrective of posture unless it can be done in
good form. Letting the body slowly down to full arms' length
from the position uses the same muscles more mildly, and this
may be used to develop strength for the chinning movement, the
subject standing on a bench to get the higher position and stepping
off to let himself down. Lifting the legs during the exercise pre-
vents it from producing chest expansion because it brings into
action muscles that hold the ribs down.

Climbing Rope. — Climbing rope, if done with the aid of the feet
and legs to grasp the rope, gives the same exercise for the arms as
chinning the bar; if the legs are not used it is much more vigorous
because the weight of the body must be held momentarily by one
arm and then the other. Swinging on the travelling rings is similar
but milder.

Cross Rest. — Cross rest on the parallel bars (German) is a familiar
exercise to develop the extensors of the elbow and depressors of the
humerus. The position is usually gained by a spring from the
floor to make it easier for the two muscle groups just mentioned,
but they are brought into use strongly in the last part of the lift
of the body and must maintain vigorous contraction to keep the
balance. Swinging legs and body forward and backward and walk-
ing forward and backward along the bars on the hands are among
the various movements used to add to the vigor of the work. To
hold one's position securely he must maintain an accurate balance
between the relative force of contraction of the pectorals and the
latissimus as the body weight is shifted (Fig. 78).

GAMES AND SPORTS.

Rowing. — Rowing is one of the simplest exercises for the arms.
It consists of two parts; a rather mild forward push combined with
arm depression and a stronger pull.

Beginning with arms flexed and body inclined well backward,

GAMES AND SPORTS 133

the first part involves the triceps, pectorals, anterior deltoid and
upper serratus to push the handle of the oar forward, the lower
pectoralis major acting also as an arm depressor to lift the other
end of the oar. If the outer end of the oar is heavy the deltoid
may be left out of the work, since it tends to raise the arm as well
as to advance it. During this phase of the movement the wrists
are sometimes flexed to "feather" the oar.

B ■Kt*

' ^^^

Ki, ' ^| '. ■■''i~.:-:.,'-'; ^B

Fig. 79. — The starting position in putting the shot.

As the forward motion is completed a relaxation of the pectorals
lets the oar drop into the water and then the pull begins. Flexion
of the elbow by the biceps group is combined with depression and
backward movement of the humerus, produced by action of the
latissimus, teres major and rhomboid, and the posterior deltoid.

Basketball. — The use of the arms in basketball consists princi-
pally of raising them to intercept or catch the ball and of throwing

134 MOVEMENTS OF ELBOW AND FOREARM

the ball by a forward movement, sometimes combined with exten-
sion of the elbow. There is a great deal of variation but the triceps
and elevators of the arms, with the upper pectoral and serratus in
the forward throw, have the main part of the work.

Volley Ball. — In volley ball the work of the triceps and arm-
raising group is more prominent, since the ball is always batted
and more often upward than in any other direction.

Bowling. — In bowling the ball is sent forward by a forward swing
of the arm, using the arm-raising muscles.

Fig. 80. — Starting position of the arms in serving.

Putting tjhe Shot. — Putting the shot, like bowling, is mainly work
for one arm. The object is to send the heavy shot as far as possible
and this requires it to be elevated at an angle of about 45 degrees.
The rules require that it shall be pushed from the chest, no swing-
ing or throwing movements of the arm being allowed.

In preparation for putting the shot is held close to the shoulder,
the elbow completely flexed and the arm and shoulder held well
back. This position puts the anterior deltoid, pectorals, and ser-
ratus on a stretch and in a favorable condition for strong action.
Strong and quick contraction of these muscles and the triceps
extends the arms diagonally- upward and projects the shot into
the air.

Batting. — Batting in baseball and cricket is a form of striking,
the club or bat being held in both hands and swung forward and

GAMES AND SPORTS 135

across the body. Right-handed batters stand with the left side
toward the pitcher and hold the bat with the right hand upper-
most. The bat is swung over the right shoulder in preparation for
striking, and when the ball comes it is swung to left to meet it.

Batting requires strong use of the flexors of hands and fingers to
grasp the bat, action of the triceps of both arms to extend the elbows,
with a different motion of the two upper arms. The right arm is
swung across the chest by the anterior deltoid and pectoral, sup-
ported by the serratus; the left arm is swung sideward and back-
ward by the latissimus, teres major, and posterior deltoid. The
trapezius acts on the right to aid the serratus and deltoid in rais-
ing the arm, while the rhomboid is in action on the left to support
the teres major.

Serving. — Serving in tennis is a form of striking in which one
arm is used. The movement begins with the arm that holds the
racket held back of the head, with elbow flexed, wrist overextended
and flexed laterally, and humerus slightly above shoulder level and
drawn well back. The ball is struck forward, the racket hitting it
at a point directly above the head. The flexors of the wrist, triceps,
and pectoral, supported by the upper serratus and aided somewhat
by the latissimus and teres major, do the work.

To give the ball the spin that makes it curve, the racket hits it
a diagonal blow in such a way that the ball travels across the face
of the racket while in contact with it. In the form of stroke just
described and shown in the figure, the drop curve can be produced
by an extension of the elbow, the racket moving upward as well as
forward while in contact with the ball.

Archery. — Archery, or shooting with bow and arrow, employs
the arm elevators of both sides, holding the arms well up so as to
bring the hand that grasps the arrow and bowstring near the ear.
The flexors of the elbow are used on one side and the extensors on
the other. The upper arms are both drawn backward strongly,
but the raised elbow on the string side and the lowered elbow on
the bow side bring into action different muscles — trapezius and
middle and posterior deltoid on one side and latissimus, teres major,
and rhomboid on the other.

QUESTIONS AND EXERCISES.

1. Pick out an ulna from the bones of a dismembered skeleton; point out the
olecranon; the styloid process; show how it articulates with the humerus, and tell
whether it is from the right or left arm.

2. Pick out a radius from the bones, point out its head, styloid process, and
bicipital tuberosity, and tell whether it is from the right or left arm.

3. Mention a movement in which the biceps acts along with the triceps; along
with the pronator teres; along with the infraspinatus; along with the middle deltoid;
along with the upper pectoralis major.

136 MOVEMENTS OF ELBOW AND FOREARM

4. Explain why a lady seldom holds her head up straight while combing her
hair; how can it be made an exercise for improving posture of the shoulders? What
muscles will be used most strongly?

5. Name the kinds of sport that tend to develop one arm more than the other;
those that tend to develop both arms but in different ways; those that develop both
arms but keep them too much in front of the chest and thus induce round shoulders.

6. When the arm-depressing muscles are used in driving nails, which way do they
tend to rotate the humerus? Is this rotation useful or a hindrance in driving nails?
What muscles are there that can prevent this rotation? Do they contract in this
movement or not?

7. When one strikes two dumb-bells together forward at the level of the shoulders,
what movement of the elbow-joint does the hitting of the bells tend to produce?
What prevents it? When will muscles act to aid? What muscles can do it? See
if they act.

8. With a tape line measure the girth of the forearm at the largest place (1) when
the hand is closed firmly as possible, (2) when the hand is opened widely as possible,
(3) when it is left relaxed. Explain the variation in girth.

9. Show a case of supination of the hand in which the biceps is not in action, and
explain why this muscle does not act and what produces the supination.

10. Does folding the arms behind the back tend to induce erect posture or not?
Explain.

CHAPTER VII.
MOVEMENTS OF THE HAND.

The muscular mechanisms of the shoulder, elbow, hip, knee and
ankle are to be seen in very similar form in most vertebrate animals,
but the hand is possessed by man alone. The hand is capable of a
greater variety of movements than any other muscular mechanism,
and this gives man his mechanical superiority over other animals.
Many animals excel man in ability to run, jump, swim, climb, and in
other movements of the larger joints, but the superior mobility of
the hand enables man to excel them all in the handling of objects
and in the ability to make and use tools. His greater intelligence is
of course the chief reason why man so far excels the other animals
in constructive ability, and yet this is in part due to his possession
of this most perfect of all mechanical instruments.

The hand includes twenty-seven bones and over twenty joints,
while its action involves the use of thirty-three different muscles.
Still the mechanism is not so difficult to comprehend as these figures
might suggest, because the five fingers are constructed on the same
general plan and the joints permit of only flexion and extension, with
a limited amount of lateral motion in three instances. The larger
muscles acting on the hand are located in the forearm and are con-
nected with their insertions by long slender tendons. These tendons
are held within a small space at the wrist by a deep concavity on the
anterior surface of the carpal bones and by a flat encircling band of
connective tissue known as the annular ligament of the wrist. There
are several small muscles in the hand itself, the largest group making
up what is known as the thenar eminence on the thumb side of the
palm, and a smaller group forming the hypothenar eminence on the
ulnar side.

The twenty-seven bones of the hand form three groups: (1) the
carpal bones, eight in number, in two rows of four bones each; (2)
the five metacarpal bones, numbered beginning at the thumb, and
(3) the fourteen phalanges, in three rows, the proximal and terminal
rows containing five each and the second row four, the phalanx of
the middle row being absent in the thumb (Fig. 81). The carpal
or wrist bones are very irregular in shape and are named as follows,
beginning on the thumb side:

First row: scaphoid, semilunar, cuneiform, pisiform.

Second row: trapezium, trapezoid, os magnum, unciform.

The metacarpals are considerably larger and longer than any
of the phalanges, and the latter decrease in size toward the tips of

138

MOVEMENTS OF THE HAND

the fingers. The phalanges of the terminal row are small and pointed.
The thumb is separated from the first or index finger more widely
than the other fingers are from one another and is turned on its

Fig. 81. — Bones of the forearm and hand, back view. (Gerrish.)

axis so that flexion is somewhat toward the others rather than in the
same plane. Notice the rounded articular surfaces at the ends of
the metacarpals and phalanges.

FLEXOR CARPI RADIAL1S 139

The wrist, which connects the rest of the hand with the forearm,
has three distinct joints permitting movement of the hand: (1) the
radiocarpal joint between the radius and the first row of carpal
bones, (2) the midcarpal joint between the two rows, and (3) the
carpometacarpal joint between the second carpal row and the meta-
carpals. These joints are all condyloid in form, rotation in the
wrist being unnecessary because the free rotation of the shoulder
and radio-ulnar joints give the hand freedom to turn through 270
degrees. Starting from the straight extended position the wrist
can be flexed through from 60 to 90 degrees. The first and fifth
metacarpals can be flexed farther than those between, making it
possible to draw the two sides of the palm toward each other, forming
a cup-shaped depression in the middle of the palm. The wrist can
be overextended 45 degrees or more, making the entire movement
considerably more than a right angle. Of the two lateral movements,
that toward the little finger, called adduction of the wrist, takes
place through about 45 degrees while abduction is less free. Besides
the abduction of the whole hand just mentioned, the thumb can be
abducted separately, moving away from the fingers through about
90 degrees. The carpometacarpal joint of the thumb is so shaped
that when the metacarpal is flexed it rotates toward the fingers;
this enables the thumb to flex toward the fingers to a varying
degree to suit the work to be done. While this rotation is slight, it
aids in bringing the ball of the thumb to meet the ball of each finger
in turn, as the reader can easily observe by experimenting with his
own hand.

The joints between the metacarpal bones and the phalanges
permit flexion through about 90 degrees, but no overextension.
These joints also permit a slight degree of abduction and adduction .

MUSCLES ACTING ON THE WRIST-JOINT.

There are six muscles acting on the wrist-joint, grouped as follows :

( carpi radialis. ( carpi radialis longus.

Flexor \ palmaris longus. Extensor \ carpi radialis brevis.

[ carpi ulnaris. [ carpi ulnaris.

Abduction of the hand is produced by the combined action of the
radial flexor and extensor, while the ulnar flexor and extensor
together adduct it.

FLEXOR CARPI RADIALIS.

This muscle lies on the upper half of the front of the forearm just
beneath the skin, half-way from the brachioradialis to the ulnar
side (Fig. 70, p. 124).

140 MOVEMENTS OF THE HAND

Origin. — The inner condyle of the humerus.
Insertion. — The anterior surface of the base of the second meta-
carpal.
Action. — Flexion and slight abduction of the wrist.

PALMARIS LONGUS.

A slender muscle lying just to the ulnar side of the preceding.

Origin. — The inner condyle of the humerus. It is often absent.

Insertion. — The annular ligament of the wrist and the fascia of the
palm (see Fig. 70, page 124).

Action. — First to tighten the fascia of the palm, then to flex the
wrist.

FLEXOR CARPI ULNARIS.

Located on the ulnar side of the forearm (Fig. 82).

Origin. — The inner condyle of the humerus and the upper two-
thirds of the narrow ridge on the back of the ulna.

Insertion. — The palmar surfaces of the pisiform and unciform
bones and of the fifth metacarpal.

Action. — Flexion of the wrist. Electrical stimulation of the
flexor carpi ulnaris does not adduct the hand, but in voluntary
adduction it contracts along with the extensor carpi ulnaris,
probably to prevent the overextension the latter would otherwise
produce.

By flexing the wrist strongly against a resistance the tendons of
the three flexor muscles can be easily felt, the radialis near the middle
and the others to the ulnar side. In some subjects it serves quite
as well to make a complete flexion without resistance. Notice the
position of these tendons in Fig. 70 to show you where to look for
them.

EXTENSOR CARPI RADIALIS LONGUS.

This muscle is on the radial side of the upper forearm, just
posterior to the brachioradialis (Fig. 70).

Origin. — The lower third of the outer condyloid ridge of the
humerus.

Insertion. — The posterior surface of the base of the second meta-
carpal.

Action. — Flexion and abduction of the wrist-joint.

EXTENSOR CARPI RADIALIS BREVIS.

Situated just behind the preceding muscle.

Origin. — The outer condyle of the humerus.

Insertion. — The back side of the base of the third metacarpal.

Action. — Direct extension of the wrist.

EXTENSOR CARPI ULNARIS
EXTENSOR CARPI ULNARIS.

141

Situated on the back and ulnar side of the forearm (Fig. 82.)
Origin. — The outer condyle of the humerus and the middle third
of the narrow ridge on the back of the ulna.

Fig. 82. — Posterior surface of the forearm and hand. (Gerrish.)

Insertion. — The posterior surface of the base of the fifth meta-
carpal.

142 MOVEMENTS OF THE HAND

Action. — Extension and adduction of the wrist.

By extreme extension of the wrist the tendons of the extensor
muscles can be brought out so that they are readily felt at the back
of the wrist. The radial pair of tendons can also be brought out by
abduction of the wrist and the ulnar pair by adduction. The ulnar
pair can be felt to contract when the thumb is strongly abducted.

The force of flexion of the wrist is nearly double that of extension,
and the power of extension is lessened in the flexed position. This
fact is recognized in Jiu Jitsu.

MUSCLES MOVING THE FINGERS.

There are three muscles in the forearm that act on all four fingers
at once, two of them flexors and one extensor. They are named —

Flexor sublimis digitorum,

Flexor profundus digitorum,

Extensor communis digitorum,
meaning superficial and deep flexors and common extensor of the
fingers. Each of these muscles has four tendons going to the four
fingers, beginning at the lower fourth of the forearm, and each tendon
is acted upon by separate groups of muscle fibers, making it possible
to flex and extend the fingers separately as well as all at once.

FLEXOR SUBLIMIS DIGITORUM.

Situated just beneath the flexor carpi radialis and the palmaris
longus on the front side of the forearm (Fig. 70).

Origin. — The inner condyle of the humerus, the coronoid process
of the ulna, and a long oblique line on the middle half of the anterior
surface of the radius.

Insertion. — By four tendons which separate after passing the
wrist and go to the four fingers. Opposite the first phalanx each
tendon splits into two, which are inserted into the sides of the base
of the second phalanx (Fig. 85).

Action. — Contraction of the flexor sublimis first flexes the second
phalanx; if the movement continues after the second phalanx is
fully flexed it then flexes the first phalanx, and finally flexes the wrist.

FLEXOR PROFUNDUS DIGITORUM.

Located just beneath the flexor sublimis (Fig. 83).

Origin. — The middle half of the front and inner surfaces of the
ulna.

Insertion. — By four tendons which separate after passing the
wrist and go to the four fingers. Each tendon passes through the

FLEXOR PROFUNDUS DIGITORUM

143

split in the corresponding sublimis tendon and is inserted into the
posterior surface of the base of the last phalanx (Fig. 85).

Action. — Flexion of the third phalanx. If the movement con-
tinues after the third phalanx is flexed it then flexes the second
phalanx, then the first and finally the wrist.

Fig. 83. — The flexor profundus digitorum. (Gerrish.)

Although the flexors sublimis and profundus each forms a single
muscular mass, the separate tendons to the fingers are moved by
separate groups of muscle fibers, so that it is possible to flex the
fingers separately. The wide difference that we see in the abilities
of different persons to do this is due to differences in coordination
resulting from various amounts and kinds of training and not from
differences in the structure of the muscles.

144 MOVEMENTS OF THE HAND

The flexor tendons pull on the wrist with a longer leverage than
on the phalanges to which they are inserted, especially after the
fingers are partly flexed, thus tending to flex the wrist every time one
flexes the fingers strongly. Flexion of the wrist slackens the flexor
tendons and thus lessens the power they can exert on the fingers,
so that we must keep the wrist extended if we wish to clench the
fist or grasp anything firmly with the hands. This is provided for
without our being aware of it by contraction of the extensors of the
wrist whenever one flexes the fingers forcibly. By placing the finger
tips on the back of the lower forearm close to the ulna one can feel
the extensor carpi ulnaris contract every time the fingers are flexed.
Paralysis of the extensors of the wrist therefore makes it impossible
to flex the fingers forcibly. Notice how feeble the flexion of the
fingers becomes when you hold the wrist in a flexed position and how
much stronger it is when you change it to a position of overextension.

EXTENSOR COMMUNIS DIGITORUM.

Situated on the middle of the back side of the forearm (Fig. 82) .

Origin. — The outer condyle of the humerus.

Insertion. — By four tendons which separate after passing the
wrist and go to the four fingers. Each tendon is attached by fibrous
slips to the back of the first phalanx and then divides into three
parts; the middle part is inserted into the posterior surface of the
base of the second phalanx and the other two unite to form a tendon
which is inserted into the posterior surface of the base of the third
phalanx.

Action. — Contraction of the extensor communis first extends the
first phalanx and then extends the wrist. If the first phalanx is held
flexed the muscle will extend the other phalanges, but if the first
phalanx or the wrist are allowed to extend its contraction has little
effect on the last two phalanges. This is partly due to the insertion
of the tendons into three successive segments of the finger and
partly to leverage and slack, as explained in case of the flexors.
Since the extensor communis has the best leverage on the wrist,
- strong extension of the fingers is impossible unless the wrist is pre-
vented from overextending as the muscle contracts. Notice how
feeble and incomplete extension of the fingers you can make with
an overextended wrist and how much better the action is when you
hold it partly flexed. By placing the finger tips on the front of the
lower forearm one can easily feel the flexor carpi radialis and the
palmaris longus contract every time a strong effort is made to
extend the fingers.

The extensor communis also separates the fingers as it extends
them. It is not able to move the fingers independently to the same
degree as the flexors because of three fibrous bands that connect

EXTENSOR COMMUNIS DIGITORUM 145

the tendons across the back of the hand (Fig. 82) . The ring finger
is especially limited in this way. As a partial remedy for this con-
dition there are two small muscles lying one on each side of the
extensor communis and providing independent extension for the
index and little fingers. They are named extensor indicis and
extensor minimi digiti, and their tendons join the tendons of the
extensor communis opposite the first phalanx of the finger to which
they belong.

Fig. 84. — Isolated action of the extensor communis digitorum, extending the
first phalanx of the fingers and the wrist without extending the secondhand third
phalanges. (Duchenne.)

Enough has been said to show that the names of the three muscles
we have just been considering are misleading if we try to apply
them in an exact way to the actions they perform. They are in fact
flexors and extensors of certain segments of the fingers rather than
of the fingers as a whole. What is more, the parts acted upon by
the flexors sublimis and profundus are not the same as those prin-
cipally controlled by the extensor communis, so that the posture of
the hand when at rest, if caused by the elastic pull of these muscles
alone, would not give the familiar normal posture but instead the
"claw-hand" shown in Fig. 86. Notice that the peculiarities of this
ungraceful position consist of a flexion of the last two phalanges,
which is the action of the two common flexors, and extension of the
first phalanx, the proper action of the extensor communis.

There are three groups of small muscles placed in the hand itself
that help to flex and extend the fingers and also to adduct and
abduct them. There are eleven of these muscles, as follows:

Four lumbricales.

Four dorsal interossei.

Three palmar interossei.
10

146

MOVEMENTS OF THE HAND

The lumbricales are in the palm and the interossei lie between the
metacarpal bones. The action of the entire eleven on flexion and
extension is the same.

Fig, 85, — Muscles of the right palm, (.Gerrish.)

THE PALMAR INTEROSSEI 147

THE LUMBRICALES.

Four little spindle-shaped muscles, named from their resemblance
to an earthworm (lumbricus). (Fig. 85.)

Origin. — The tendons of the flexor profundus digitorum.
Insertion. — The tendon of each muscle turns around the radial
side of the metacarpal bone and is inserted into the tendon of the
extensor communis.
Action. — To flex the first phalanx and extend the second and third.

■
THE DORSAL INTEROSSEI.

Four small muscles lying between the five metacarpal bones at
the back of the hand.

Origin. — Each from the two bones between which it lies.

Insertion. — The base of the first phalanx and the tendon of the
extensor communis for each finger.

Action. — To abduct the fingers away from the middle finger, to
flex the first phalanx and to extend the second and third.

THE PALMAR INTEROSSEI.

Three small muscles in the palm, on the central sides of the second,
fourth, and fifth metacarpals (Fig. 71).

Origin. — Sides of the metacarpals except the first and third.

Insertion. — Same as the dorsal interossei, but on the inner rather
than the outer surfaces of the phalanges.

Action. — Adduction of the fingers, flexion of the first phalanx and.
extension of the second and third.

The muscles that act on the hand are controlled through three
nerves, the ulnar, median and musculospiral nerves. The ulnar
supplies the ulnar flexors and extensors, the lumbricales and inter-
ossei that lie on the ulnar side of the midfinger, and a part of the
flexor profundus. The median supplies the other flexors and the
musculospiral the other extensors. Interesting light is thrown on
the action of these muscles by the forms of paralysis resulting from
disease and injury of these nerves.

Ulnar paralysis frequently involves the lumbricales and inter-
ossei. When these muscles are paralyzed, especially when no other
muscles are involved, the hand takes the claw-like form shown in
Fig. 86. The explanation is that when the normal tone of lumbri-
cales and interossei is gone the unopposed tension of the extensor
communis pulls the first phalanx into a position of overextension
while the flexors sublimis and profundus for the same reason produce
pronounced flexion of the other two phalanges. Any attempt of

148 MOVEMENTS OF THE HAND

the patient to flex or extend his fingers only exaggerates the deform-
ity. The hand is useless, for without the ability to flex the first
phalanx it is impossible to close the hand or grasp anything between
the fingers and thumb. Recovery frequently occurs, and then the

Fig. 86. — Claw-shaped hand resulting from paralysis of the lumbricales and interossei
caused by an injury to the ulnar nerve. (Duchenne.)

claw form is gradually lost and the posture of the normal resting
hand resumed, as the small muscles gradually take on normal vigor
and tone.

Another condition that makes it impossible to close the hand or
grasp an object with fingers and thumb is paralysis of one or both
of the long flexors of the fingers. Fig. 87 shows the effect on the
posture of the hand of paralysis of the middle half of the flexor

Fig. 87. — Deformity of middle and ring fingers caused by paralysis of the middle
half of the flexor sublimis digitorum. (Duchenne.)

sublimis. Here it is the normal tension of the lumbricales and inter-
ossei that is unopposed, and the second phalanx is pulled into marked
overextension. If the paralysis affects the profundus, it is the
terminal phalanx that is drawn out of normal position.

-THE PALMAR INTEROSSEI 149

Another class of cases of paralysis of the hand is due to lead
poisoning. This affects the musculospinal nerve. The extensor
communis is most often paralyzed; the extensors of the wrist less
often.

When the extensor communis is alone paralyzed the resting posi-
tion of the hand is characterized by marked flexion of the first
phalanx, caused by the unbalanced tension of the lumbricales and
interossei. Flexion of the fingers is nearly normal, so that the ordi-
nary uses of the hand to grasp and carry objects is not abolished as
in paralysis of the flexors or the small muscles of the hand. The
second and third phalanges can be extended but not the first.

Paralysis of the extensor communis causes one peculiar defect
that has always puzzled physicians. The patient can flex and
extend his wrist readily when his fingers are flexed, and this is what
one would expect, for in the class of cases we are considering the
flexors and extensors of the wrist are normal. But if the patient
tries to extend his fingers his wrist takes a flexed position and he
cannot extend it. The extensor communis being paralyzed, the
only muscles he can bring into action to extend his fingers are the
lumbricales and interossei, which acting alone flex the first phalanx
while they extend the second and third. What causes the flexion
of the wrist?

Attention has been called to the fact that in normal extension
of the fingers the action of the extensor communis is always accom-
panied by a contraction of the flexors of the wrist. This seems to be
an inherited coordination so firmly fixed in the nervous system that
individuals cannot leave the wrist flexors out of the performance
even if they wish to do so. This, as suggested by Beevor, is probably
the explanation of the case just mentioned. When the person with
paralyzed extensor communis tries to extend his fingers he uncon-
sciously brings into action the entire group normally used in the
movement. Realizing his inability to completely straighten the
fingers he makes an unusually strong effort which brings the wrist
flexors strongly into action and inhibits the wrist extensors. Under
normal conditions this serves to balance the strong pull of the
extensor communis on the wrist, but as the communis does not act
the wrist is so strongly flexed that contraction of the wrist extensors
cannot overcome it. The extension of the last two phalanges also
takes up slack in the tendons of the long flexors of the fingers and
this probably helps to keep the wrist flexed.

A common test for lead poisoning is to support the forearm in a
pronated position with the hand and wrist unsupported and see how
much the latte** drop down from the weight of the hand. Paralysis
of the extensor muscles greatly increases the extent of the " wrist-
drop" and so indicates something of the presence and severity of the
poisoning.

150 MOVEMENTS OF THE HAND

MUSCLES MOVING THE THUMB.

Of the eight muscles moving the thumb, four are in the forearm
and four in the thenar eminence, commonly called the "ball of the
thumb." Some of these muscles correspond to muscles that act on
the fingers, and it will help in understanding and remembering the
new ones to keep such resemblances in mind.

Three of the four muscles of this group that are located in the
forearm are extensors of the thumb, one for each of its three
segments.

EXTENSOR LONGUS POLLICIS.

The extensor longus pollicis lies on the back of the forearm next
to the extensor indicis and like it may be considered as a part of the
extensor communis digitorum. The tendon is shown in Fig. 82.

Origin. — Posterior surface of the middle third of the ulna.

Insertion. — The posterior surface of the base of the last phalanx of
the thumb.

Action. — It extends the last phalanx of the thumb and then if the
movement is continued it extends the other joints, drawing the
thumb into the plane of the rest of the hand. The tendon of the
extensor longus pollicis lacks the attachment to the first phalanx
found in the extensor communis and consequently it extends
especially the last phalanx, which the common extensor fails to do.

EXTENSOR BREVIS POLLICIS.

This muscle lies deep beneath the extensor communis on the back
of the forearm.

Origin. — Small spaces on the back of both radius and ulna near
their middle.

Insertion. — The posterior surface of the base of the first phalanx
of the thumb.

Action. — Extension of the first phalanx. When the movement is
strongly made the whole thumb is abducted and the extensor carpi
ulnaris comes into action to prevent abduction of the wrist.

EXTENSOR OSSIS METACARPI POLLICIS.

This, the last of the long extensors, acts, as its name indicates,
on the metacarpal bone of the thumb. It lies just toward the radial
side of the preceding muscle. Sometimes called " long abductor of
the thumb."

Origin. — A small space on the ulnar side of the radius near its
middle.

FLEXOR BREVIS P0LL1CIS 151

Insertion. — The posterior surface of the base of the first metacarpal.

Action. — To extend or abduct the metacarpal bone of the thumb.
Its action on the whole thumb is very much like the preceding
muscle, but it pulls a little more toward the back of the hand. The
extensors of the thumb have very little to do with the act of grasping
objects, which is the most important action of the hand. Paralysis
of these muscles allows the thumb to be drawn so far inward by the
muscles of the thenar eminence that it is in the way of closing the
fingers.

There are three flexors of the thumb, corresponding to the three
extensors in that there is one for each segment.

FLEXOR LONGUS POLLICIS.

This is the only flexor of the thumb located in the forearm. Since
the thumb lacks the second phalanx the flexor sublimis, flexor of the
second phalanx of the fingers, naturally has no counterpart among
the thumb muscles. The flexor longus pollicis lies beside the flexor
profundus in the forearm and is attached to the last phalanx like
the latter. It can therefore be considered as a part of the deep
flexor (Fig. 83).

Origin. — Anterior surface of the middle half of the radius.

Insertion. — The anterior surface of the base of the last phalanx of
the thumb.

Action. — To flex the last phalanx of the thumb. Loss of this
muscle makes it impossible to grasp an object forcibly between the
encfs of the thumb and fingers and so interferes seriously with some
of the finer uses of the hand, such as sewing, knitting, drawing,
painting, etc. It has little or no influence on the other joints of the
thumb.

The two short flexors of the thumb lie side by side in the thenar
eminence, the flexor brevis toward the palm and the flexor ossis
metacarpi pollicis external to it and toward the wrist (Fig. 88).
The abductor pollicis covers most of the two, but a small part of
the flexor brevis projects from under its palmar edge.

FLEXOR BREVIS POLLICIS.

This is the inner of the two short flexors.

Origin. — The trapezium and the front side of the annular ligament.
Insertion. — Base of the first phalanx of the thumb.
Action. — Flexion of the first phalanx, and movement of the entire
thumb toward the little finger.

152

MOVEMENTS OF THE HAND

FLEXOR OSSIS METACARPI POLLICIS.

Formerly called the "opponens pollicis" or opposing muscle of
the thumb (Fig. 88).

Fig.[88. — Muscles of the right palm. (Gerrish.)

ADDUCTOR POLLICIS 153

Origin. — The trapezium and the annular ligament.

Insertion. — The shaft of the metacarpal bone on its radial side.

Action. — Flexion and inward rotation of the metacarpal, and with
it the whole thumb. By its use the tip of the thumb can be made to
meet the tips of the four fingers in turn.

The two remaining short muscles of the thumb are the abductor
and adductor pollicis, corresponding closely to the interossei of the
fingers.

ABDUCTOR POLLICIS.

This is the most superficial muscle of the ball of the thumb and is
on the side of the thumb opposite the first finger (Fig. 85.)

Origin. — The trapezium and scaphoid bones and the annular
ligament.

Insertion. — The outer surface of the base of the first phalanx of
the thumb and into the tendon of the extensor longus pollicis.

Action. — To draw the thumb away from the first finger, move the
second phalanx laterally, and to extend the last phalanx. At the
same time it rotates the thumb inward, placing it in opposition to
the fingers. This is not considered a true rotation, such as takes
place in a ball-and-socket joint, but the shape of the articular
surfaces produces a small degree of rotation when the metacarpal
is flexed or abducted.

ADDUCTOR POLLICIS.

This is the deepest of the thenar muscles (Fig. 71).

Origin. — The os magnum, the annular ligament and the lower
two-thirds of the third metacarpal bone.

Insertion. — The inner surface of the base of the first phalanx of
the thumb and the tendon of the extensor longus pollicis.

Action.— To draw the thumb toward the first two fingers, move
the first phalanx laterally and extend the last phalanx.

Experts on accident insurance estimate the value of the thumb
at half that of the whole hand. Its usefulness is largely due to its
position of opposition to the fingers and the resulting ability to grasp
and hold objects between them. In the finer work in which man
excels other animals certain tools are moved by action of the fingers
and thumb. In this work it is the muscles of the thenar eminence
that are of greatest value in moving the thumb. The hand of man
differs from that of the anthropoid apes mainly in the greater
development of the muscles of the thenar eminence and in the
habitual position of the thumb, which is one of much more complete
opposition to the fingers.

154 MOVEMENTS OF THE HAND

FUNDAMENTAL MOVEMENTS OF THE HAND.

In forcible closing of the fist the flexors of the fingers and thumb
and the abductor pollicis are used and also the extensors of the
wrist.

In the simplest but strongest uses of the hand, such as grasping
the rungs of a ladder or hanging by the hands from a bar, the most
of the work is done by the flexors sublimis and profundus working
with the extensors of the wrist. The flexors of the thumb help more
or less, depending on the size of the bar and the consequent need of
holding it firmly to the palm. With a small bar gymnasts often
leave the thumb free.

In chopping and in using a hammer there is also strong adduction
of the wrist. In the use of coarse tools, such as the axe, hammer,
saw, plane and wrench, it is mainly the three flexors of the thumb
that come into action. In finer work, such as the use of a pen,
pencil, needle, or other small instruments, where the tips of the
thumb and fingers must be brought together, it is necessary to keep
the thumb in a position of abduction and flex the first phalanx of
the fingers to nearly a right angle, because the thumb is so much
shorter than the fingers. Duchenne points out the interesting fact
that when the abductors of the thumb are paralyzed and the thumb
flexors have to bring it into opposition to the fingers alone, the tip
of the thumb meets the second phalanx of the fingers, unless the
second and third phalanges of the latter are sharply flexed, and this
renders the hand very clumsy and reduces its ability to do fine work
accurately or rapidly.

Writing with a pen or pencil and using the so-called "finger
movement" requires the use of many muscles. The grasping of the
pen between the thumb and the next two fingers calls into action the
flexors profundus and sublimis. The three flexors of the thumb
along with the abductor are likewise required. To make an up-
stroke with the pen the lumbricales and interossei contract and
extend the last two phalanges while still further flexing the first;
in the thumb a similar movement takes place, the metacarpal bone
being flexed on the wrist and the other joints extended. Then to
make a down-stroke the two flexors of the fingers join with the
extensor communis in order to pull the finger tips closer to the palm,
while the extensor ossis metacarpi pollicis acts with the flexors
longus and brevis pollicis to accomplish the same on the thumb side.

PART III.

THE LOWER LIMB.

CHAPTER VIII.
MOVEMENTS OF THE HIP-JOINT.

Everyone is familiar with resemblances between the upper and
lower limbs, so great that they seem to be constructed on the same
general plan, and the reader will perhaps notice some resemblances
new to him as we proceed. We are met at the outset, however,
with a marked difference in that the pelvic girdle, which corre-
sponds to the shoulder girdle, is not movable like the latter, with
the consequence that the entire set of movements and muscles
studied in Chapter IV has no counterpart in the lower limb.

The pelvic girdle consists of three bones : the ilium above and at
the side of the hip, the pubes below and forward, the ischium below
and backward. These three bones are separate in early life, but in
the adult they are joined to make one solid bone — the hip bone.
Each hip bone joins the hip bone of the opposite side at the front
of the pubes and each joins the sacrum at the rear, forming the
pelvic basin or pelvis. The three articulations just mentioned do
not permit any considerable movement, and hence are held together
by ligaments only. The sacrum is a solid bone formed by the fusion
of five vertebra?; the spinal column rests upon its summit and is
joined firmly to it.

The hip-joint is formed by the articulation of the head of the
femur with the acetabulum, which is the name given to the socket
on the outer surface of the hip bone just where the ilium, pubes
and ischium join. It is a ball-and-socket joint, having less freedom
of motion than the shoulder-joint, the socket being deeper and the
bones fitting so closely that much force is required to pull it apart.
The usual capsular ligament is present and is thickened on the
front side by an A-shaped band called the iliofemoral band or the
inverted Y-ligament (Fig. 90).

156

MOVEMENTS OF THE HIP-JOINT

The femur is the longest bone in the body and corresponds in a
way to the humerus; like the humerus it has a head, shaft, and two
condyles; in place of tuberosities it has two large prominences, the
great and small trochanters; along the back of the shaft is the
linea aspera, or rough line.

The hip-joint permits movement of the femur most freely for-
ward, and therefore this is called flexion; it can take place through
150 degrees or more, when it is stopped by contact of the thigh
with the front of the trunk. When the knee is extended the hip-

POSTERIOR SUPE
RIOR SPINE

POSTERIOR IN
FERIOR SPINE

ANTERIOR SUPE-
RIOR SPINE

ANTERIOR IN-
FERIOR SPINE

SPINE OF

ISCHIUM

SMALL SCIATIC

NOTCH

Fig. 89. — The hip bone of right side, outer surface. (Gerrish.)

joint can be flexed only to the extent of a right angle, but this is
due to tension of the hamstring muscles and not to the form of the
joint.

The reverse of flexion, movement of the femur downward and
backward, is called extension, and is free until the limb is vertically
downward in line with the trunk, when it is stopped by tension
of the iliofemoral band and of the psoas and iliacus muscles,
making any overextension of the hip impossible in normal subjects.
Careful examination will show that in apparent overextension of

MOVEMENTS OF THE HIP-JOINT

157

the hip, which occurs when one pushes one limb as far back as
possible while standing on the other limb, the pelvis tilts back
with the moving femur, the movement really being a slight flexion
of the other hip and slight overextension of the spinal column in the
lumbar region. The fact that we bend forward to reach the floor
but not backward is due to the impossibility of overextending the
hip-joints.

Fig. 90. — Right hip-joint, front view. (Gerrish.)

Movement of one limb away from the other toward the side is
called abduction, and is usually possible through 45 degrees or
more. The limitation here is due to resistance of opposing muscles,
the joint itself permitting nearly 90 degrees of abduction, especially
if the toes are turned outward. Abduction may also take place
by movement of the trunk; for example, the right hip-joint is
abducted by inclining the trunk to the right while standing on
the right foot. Adduction is limited by contact of the moving
limb with the other limb; it can take place further when the mov-
ing limb is a little front or rear from the other, or when the trunk
is inclined to the side, as in the last example; the right hip is also
adducted when the left hip is dropped below the level of the right
while standing on the right leg.

158

MOVEMENTS OF THE HIP- JOINT

Movement of the limb in a circular manner by a combination of
the four movements above described is called circumduction; turn-
ing the limb on its central axis is called rotation. This axis is a
line through hip-, knee-, and ankle-joints, passing considerably
inside of the shaft of the femur because of the sharp bend of that
bone near the trochanters. Rotation is possible through about
90 degrees, and is said to be outward or in-
ward according to the way the toes are
turned. Because of the sharp bend of the
femur just mentioned the head of the bone
rotates in the joint in the movement called
flexion, and the neck of the femur strikes the
side of the socket and limits the movement
called rotation of the limb. One can easily
see by noticing the way the bones come in
contact why flexion is so free and why rota-
tion is so limited.

There are sixteen muscles acting on the
hip-joint besides a group of six smaller ones ;
they are classified for our purposes as fol-
lows : Practically all of them have some less
important action that will be explained as
we study them individually, the grouping
here being to help the beginner get a grasp
on the main facts.

Six flexors: psoas, iliacus, sartorius, pec-
tineus, rectus femoris, tensor.

Four extensors: gluteus maximus, biceps,
semitendinosus, semimembranosus.

Two abductors: gluteus medius, gluteus
minimus.

Four adductors: adductor gracilis, ad-
ductor longus, adductor brevis, adductor
magnus.

Six outward rotators: pyriformis, obturator
t,,,., externus, obturator internus, gemellus supe-

rear view. '(GerrST' rior> gemellus inferior, quadratus femoris.

PSOAS.

Nearly all of the psoas lies in the abdominal cavity behind the
internal organs, where it cannot be easily observed during life. It
is usually called the "psoas magnus" to distinguish it from a small
muscle associated with it in most vertebrate animals and called the
"psoas parvus," The latter muscle has no utility in an animal

PSOAS

159

that stands erect, and is therefore an undeveloped rudiment in
man.

Origin. — The sides of the bodies of the last dorsal and all the
lumbar vertebrae.

Insertion. — The small trochanter of the femur.

Structure. — Muscle fibers arising
directly from the bodies of the verte-
brae and attaching obliquely into the
tendon of insertion.

Action. — The line of pull of the
psoas is indicated by a string tied
around the shaft of the femur, with
the knot just below the small tro-
chanter and the free end held beside
the bodies of the lumbar vertebrae,
passing across the front of the pelvis
in a notch just in front of the hip-
joint. Notice that the small tro-
chanter, while it is on the inner side
of the femur, is so nearly on the axis
of rotation that the psoas can have
little rotary effect, and that the pull
is so directly across the front of the
joint that it will tend to flex the hip.

Looking at the string used to repre-
sent the psoas from a position at the
side of the skeleton, we can see that
the origin of the muscle is farther to
the rear than its insertion, that it
makes a considerable angle where it
pulls across the edge of the pelvis,
and that as a result it pulls forward
on the femur at a fairly favorable
angle in spite of the fact that its ori-
gin is so far back. By lifting the
femur forward and upward and notic-
ing the angle of pull it is apparent
that the leverage improves as the
limb is raised. The turn across the

front of the pelvis also gives the psoas considerable leverage in
pulling the spinal column forward.

Duchenne reports that he was unable to get isolated action of
the psoas, and it is practically impossible to observe its action on
a normal subject. It appears to be in a position to flex the hip,
and especially well adapted to work where hip and spinal column

Fig. 92. — Superficial muscles of the
front of the thigh. (Gerrish.)

160 MOVEMENTS OF THE HIP-JOINT

are flexed at the same time, as in climbing rope and similar exer-
cises. It is so closely associated with the next muscle that further
statement will be made along with the latter.

ILIACUS.

Named from the bone on which it has its origin.

Origin. — The inner surface of the ilium and a part of the inner
surface of the sacrum near the ilium.

Insertion. — Its tendon joins that of the psoas just where the latter
crosses the front of the pelvis, to attach with it on the small
trochanter.

Structure. — Muscle fibers arising directly from the ilium and
joining the tendon obliquely.

Action. — The junction of the iliacus to the tendon of the psoas
indicates a common action, except that the iliacus cannot flex the
trunk. Duchenne states that in a few thin subjects he was able to
stimulate the iliacus and that he secured in that way a powerful
flexion of the hip-joint with a slight and weak outward rotation of
the limb. This sets aside any doubt we might have as to the action
of the two muscles and makes it highly probable that the two,
which Duchenne suggests be named the "iliopsoas," act to flex the
hip in all exercises, like walking, running, jumping, and climbing.

SARTORIUS.

The name means "tailors' muscle," because the ancient anato-
mists noticed that it is the muscle used in crossing the legs to take
the position Oriental tailors assume at their work. It is the longest
muscle in the body, and is capable of greater extent of contraction
than any other.

Origin. — The notch between the two anterior spines of the ilium.

Insertion. — Lower front part of the inner tuberosity of the tibia.

Structure. — Parallel longitudinal fibers. The muscle lies between
two layers of the fascia of the thigh, and some of its fibers are
inserted into the fascia half-way down the thigh. The muscle
curves around the inner side of the thigh, passing behind the inner
condyle and then forward to its insertion.

The fascia of the thigh is a thick sheet of fibrous connective
tissue that envelops the thigh just under the skin.

Action.- — The position of the sartorius, curving around the front
and inner sides of the thigh, makes it difficult to learn much of its
action by a study of the skeleton. Its isolated action, under the
influence of electricity, flexes both the hip and the knee, as one
would expect from its general position. It is not difficult to observe

RECTUS FE MORIS

161

the action of the sartorius on the living body, although its appear-
ance in action is unusual, as it draws down into the mass of muscle
beneath it when it contracts, forming a deep furrow down the inside
of the thigh. It also pulls up on the fascia and the skin, forming a
set of wrinkles for a distance of 2 or 3 inches below the groin.
It acts in walking, running, and all movements combining flexion
of the hip and knee.

Fig. 93.-

-Muscles of the hip in action: S, sartorius; R, rectus femoris; G, gluteus
maximus; g, gluteus medius; V, vastus externus.

RECTUS FEMORIS.

This large muscle, named from its position straight down the front
of the thigh, corresponds closely to the long head of the triceps on
the arm, being the middle part of a three-headed extensor.

Origin. — The antero-inferior spine of the ilium, between its tip
and the hip-joint.

Insertion. — The upper border of the patella.

Structure. — The upper tendon passes down the middle of the
muscle and the flattened lower tendon passes up beneath its deeper
surface ; the muscle fibers cross obliquely from one tendon to the other.
11

162 MOVEMENTS OF THE HIP-JOINT

Action. — A cord looped around the patella and the free end held
against the ilium just in front of the hip-joint shows the direction
of pull; plain tendency to flex the hip, but a very short power
arm and a pull nearly in line with the femur, favorable for speed
but not for force; there is very little change in leverage when the
limb is lifted. Any force keeping the knee flexed will make the
tension on the rectus femoris much greater.

Isolated action of the rectus femoris causes flexion of the hip
and extension of the knee with great speed and power, giving the
motion employed in kicking a football. It is the only muscle that
could do this alone and therefore might be properly called the
"kicking muscle." It forms a conspicuous ridge down the front
of the thigh as it contracts and can be seen and felt in action in
all movements of combined flexion of the hip and extension of the
knee. Its action on the knee will be discussed further in connection
with the muscles extending the knee.

PECTINEUS.

A short thick muscle just below the groin, partly covered by the
sartorius and the rectus femoris (Fig. 92).

Origin. — A space an inch wide on the front of the pubes, just
below the rim of the pelvic basin.

Insertion. — A line about 2 inches long on the back of the femur,
extending downward from a point just behind the small trochanter.

Structure.— Penniform, both ends of the muscle having muscular
and tendinous fibers intermingled. It is twisted through 90 degrees
as it passes from origin to insertion.

Action. — A rubber band looped about the femur just below the
small trochanter and held at the point of origin shows a pull for-
ward and inward at about equal angles; its attachment to the
femur so far back seems to indicate rotation outward. Its power
arm is several inches and its angle of pull about 60 degrees, indicat-
ing lifting power rather than speed of movement. Leverage improves
as the femur is moved forward and inward.

Isolated action of the pectineus produces powerful flexion of the
hip, adduction with less force, and feeble rotation outward. The
pectineus can alone lift the thigh while the subject is sitting and
place it across the other thigh.

It is easy to observe that the pectineus acts in vigorous flexion
of the hip, whether it is combined with adduction or not. It is
used tin practically all vigorous flexion of the hip, especially in
motions requiring force rather than speed.

GLUTEUS MAXIM US 163

TENSOR.

A small muscle at the front and side of the hip, often called
"tensor fascia lata" and "tensor vaginae femoris" from its action
to tighten the fascia of the thigh. It is peculiar in having no bony
insertion (Fig. 92).

Origin. — A line about an inch and a half long just below the
anterior extremity of the crest of the ilium.

Insertion. — The fascia of the thigh, one-fourth of the way down
the outside of the thigh.

Structure. — The muscle lies between two layers of the fascia and
the longitudinal muscle fibers are inserted into these two layers.

Action. — The peculiar position of the tensor makes it difficult
to study its action on the skeleton. Early anatomists had many
disputes about its action until electric experiment settled the matter
finally, proving that it is mainly a flexor with some abducting
action and slight inward rotation. Study of defective cases also
proves that it is a strong flexor of the hip, aiding in the forward
swing of the limb in walking, with its abducting and rotating power
useful to counteract the opposite effect of other flexors, giving a
pure flexion as a combined effect of the group.

The flexor muscles of the hip, like those of the shoulder, are
more indispensable than any other group acting on the joint.
Walking is impossible without them, the subject lacking the use of
the flexors of the hip being unable to bring the foot forward to
take a step. This refutes the theory of the Weber brothers, two
famous German students of kinesiology, who taught that the
limbs swing like a pendulum without need of muscular action to
bring them forward.

When one stands at ease the flexors of the hip do not act, because
the iliofemoral band is able to prevent the trunk from falling over
backward; but if one who is standing pushes forward with the
arms against a strong resistance or in any other way brings strong
tension on the iliofemoral band, the flexor muscles at once come
into action to protect it from injury. Sensory fibers like those in
Fig. 2 probably give rise to the stimulus in such cases, the tension
on the ligament squeezing and thus stimulating the sensory end-
ings. Such action has often been called "acting in sympathy"
with a ligament or a muscle, because until recently the true cause
of the action was not known and a poetic one was assumed.

GLUTEUS MAXIMUS.

A very large fleshy muscle at the back of the hip.

Origin. — The outer surface of the ilium along the posterior one-
fourth of its crest, the posterior surface of the sacrum close to the
ilium, and the fascia of the lumbar region.

164

MOVEMENTS OF THE HIP-JOINT

Insertion. — A rough line about 4 inches long on the back of the
femur between the greater trochanter and the linea aspera.

Structure. — Muscular fibers arising directly from the pelvis and
making an oblique junction with the tendon of insertion, which is
a flat sheet extending up from the femur and along the posterior
edge of the muscle.

Action. — From time immemorial anatomists have disputed over
the action of the gluteus maximus, and the disagreement is not
surprising to one who tries to figure it out on the skeleton. It has

Fig. 94. — Gluteus maximus of right side. (Gerrish.)

been called an abductor, and adductor, and an extensor of the hip,
with all possible combinations of these movements with both kinds
of rotation. It remained for Duchenne with his electric methods
to finally determine its true action, which is powerful extension
with weak rotation outward and no adduction or abduction.

An observer can easily experiment on himself in studying the
action of the gluteus maximus, as it can easily be felt with the hand
while various movements are performed. It is easy to convince
one's self in this way that it contracts in raising the trunk from a

GLUTEUS MAXIMUS

165

position of inclination forward and from a position in which the
knees are bent deeply, and that in such cases it ceases to act before
the erect position is reached. It can be observed similarly that it
acts in walking up stairs or up a steep incline, but not in walking
on a level. These peculiarities in the action of the gluteus maxi-

Fig. 95. — The extensors of the hip in
action: G, gluteus maximus; H, ham-
string group.

Fig. 96. — Superficial muscles of the back
of the thigh. (Gerrish.)

mus are instances of a peculiar rule governing the coordination of
extension of the hip somewhat similar to one noticed as to the
upward rotation of the scapula, where the lower serratus magnus
failed to work in certain positions. The rule here seems to be that
the gluteus maximus is not called into action in extension of the
hip unless the hip is flexed more than about 45 degrees, except

166 MOVEMENTS OF THE HIP-JOINT

when there is strong resistance, when the angle of limitation is less.
The rule explains several otherwise mysterious cases, such as the
tendency of bicyclists to stoop forward, the demonstrated advan-
tage of the crouching start in sprint racing, and the tendency of
old people to incline the trunk forward in going up stairs. In all
such instances the position gives the person stronger use of the
gluteus maximus.

Persons who have lost the use of the gluteus maximus walk nor-
mally but cannot go up stairs nor up an incline without extreme
fatigue, while running, jumping, or dancing quickly exhausts them.

BICEPS.

Similar in several respects to the biceps of the arm.

Origin.— The long head from the tuberosity of the ischium; the
short head from the lower half of the back side of the shaft of the
femur, along the linea aspera and the external condyloid line.

Insertion. — The outer tuberosity of the tibia and the head of the
fibula.

Structure. — The tendon of origin is long and flat and forms a
septum between the biceps and the semitendinosus; the lower
tendon extends half-way up the thigh; the muscle fibers are short
and pass obliquely downward from the upper tendon and the femur
to join the lower tendon.

Action. — A cord drawn tight from the head of the fibula to the
tuberosity of the ischium indicates the line of pull, showing that
the muscle is in a position to extend the hip and rotate it outward
and to flex the knee. The leverage is much longer at the hip. The
short head will act only on the knee, and its main action there will
be described later.

Isolated action of the biceps extends the hip, rotates it outward,
and also flexes and rotates the knee-joint outward.

SEMITENDINOSUS.

Named from its long tendon of insertion, which reaches half-way
up the thigh; it is a close companion of the biceps.

Origin. — The tuberosity of the ischium, by a common tendon
with the biceps.

Insertion. — The lower front side of the inner tuberosity of the
tibia, along with the sartorius.

Structure. — The short muscle fibers pass diagonally downward
from the tendon of origin to join the tendon of insertion, the bulk
of the muscle being in the upper half of the thigh.

SEMIMEMBRANOSUS 167

Action. — The conditions under which the semitendinosus acts
make it plain that it can extend the hip and flex the knee just like
the biceps, but with opposite rotary action on both hip and knee.
The tendency to rotation of the hip is less than that of the biceps.

Isolated action of the semitendinosus verifies these conclusions
and shows that, like the biceps, it acts with most power on the hip.

SEMIMEMBRANOSUS.

This muscle, which is named from its knife-like shape, lies just
inside of the semitendinosus and partly beneath it.

Origin. — The tuberosity of the ischium.

Insertion. — The inner half of the posterior surface of the inner
tuberosity of the tibia.

Structure. — Similar to the preceding muscle, but a longer upper
tendon and a shorter lower one brings the muscular mass lower
down.

Action. — The conditions of action here are practically the same
as the two preceding muscles as regards the hip-joint; isolated
action indicates the most powerful action on the hip of the three.

The biceps, semitendinosus, and semimembranosus form a group
known as "the hamstring muscles." These muscles, while smaller
and less powerful extensors of the hip than the gluteus maximus
are much more useful for the ordinary purposes of life because
they act normally in walking and in standing, while the gluteus
maximus does not. The consequence is that one who has lost the
use of the gluteus maximus may stand and walk normally, while
one who has lost the hamstring muscles can stand and walk only
by throwing the weight of the trunk so far back that it tends to
overextend rather than to flex the hip, putting a tension on the
iliofemoral band. Such a position can be maintained without the
use of the hamstring group while standing still and in walking care-
fully on a smooth and level place, but one who has lost the ham-
string group cannot walk rapidly or irregularly, nor can he run,
hop, jump, dance, or incline the trunk forward without falling.

When the trunk in a normal individual is inclined forward on
the hip-joints as an axis, the knees being kept extended and the
trunk held as straight as it is in the erect position, the average
adult can incline until the flexion in the hip-joints is about 45
degrees; the hamstring muscles, somewhat shortened by contract-
ing to sustain the weight of the trunk, permit no further flexion.
One can flex one hip farther than this while standing on the other
foot, because in this position the hamstring group is relaxed and
therefore longer than in the preceding case. The same is true when
one sits on the floor with the legs out straight in front; by using

168 MOVEMENTS OF THE HIP-JOINT

all the force of the flexors most people can hold the trunk erect,
the stretched and relaxed hamstring muscles permitting a flexion
of 90 degrees. While sitting on a chair or bench there is no diffi-
culty in holding the trunk erect, because now the hamstring muscles
are not only relaxed but further slackened at the lower end by
flexion of the knee; the hips will flex several degrees farther here
and also in sitting on the floor if the knees are flexed, tailorwise.

GLUTEUS MEDIUS.

A short thick muscle situated at the side of the ilium and giving
the rounded contour to the side of the hip (Figs. 93 and 96).

Origin. — The outer surface of the ilium near its crest.

Insertion. — The back part of the top of the great trochanter.

Structure. — The fibers arise directly from the ilium and converge
to a penniform junction with the flat tendon of insertion.

Action. — It is easy to observe by reference to the skeleton that
the power arm here, which is a straight line from the top of the
trochanter to the center of the hip-joint, is an unusually long one
and that the muscle pulls upon it at almost a right angle, giving
the muscle great mechanical advantage. The vertical pull given
by the central fibers will swing the limb away from the median
line, the other parts swinging it a little to front and rear, according
to their position; some rotary action seems likely when front or
rear parts act alone.

The back part of the gluteus medius is covered by the gluteus
maximus, so that the former cannot be stimulated by electricity
entire unless the latter is gone. Duchenne found many cases in
which the atrophy of the gluteus maximus made this possible, and
he reports that the whole muscle stimulated at once gives vigorous
abduction; the anterior fibers give a combination of abduction with
movement forward and rotation inward; posterior fibers movement
backward and rotation outward. Stimulation of the successive
fibers from front to rear swings the limb first sidewise and forward,
then gives it a curving movement toward the side and then to the
rear.

GLUTEUS MINIMUS.

A'smaller companion of the preceding, lying just beneath it.
Origin. — The lower part of the outer surface of the ilium.
Insertion. — The front part of the top of the great trochanter.
Structure. — Similar to the medius.
Action. — Same as thejmedius.'sp

The"*' gluteus medius can f be felt in action in all movements
involving abduction of the hip, and it is highly probable that the

GLUTEUS MINIMUS

169

gluteus minimus joins with it. It should be noticed, as before
stated, that abduction can take place either by movement of the
limb or movement of the pelvis; this is illustrated in Fig. 97, which
shows abduction in both hip-joints, the right joint being abducted
by a sidewise swing of the right limb and the left joint by elevation
of the right side of the pelvis. When the trunk is held erect, as in
this figure, the abductors on the side that supports the weight of

Fig. 97. — Balancing on one foot, involving abduction of both hip-joints.

the body have much the greater work to do; when the trunk is
inclined to the left the center of gravity is brought more nearly
above the left hip-joint and the abductors of that side have less to do.
The very common habit of standing on one foot is a serious
menace to good posture or not, depending on the efficiency of the
two muscles just studied. If the abductors have enough tone and
power and are brought into action by the habitual coordination
to keep the pelvis at practically the same height on the two sides,

170 MOVEMENTS OF THE HIP-JOINT

little harm comes from it; but if the free hip is allowed to drop
down by relaxation of these muscles a lateral deviation of the
spinal column necessarily results, eventually causing lateral curva-
ture of the spine. It is better for this reason to form the habit of
standing on both feet instead of one, and this is particularly true
with girls and women because they have a wider pelvis and usually
less tone and strength of muscle; to make the harmful results as
slight as possible when the habit of standing on one foot is formed,
it is well to have in all gymnastic work a considerable amount of
exercise that' will tone up the abductors of the hip, such as poising
and balancing on one foot, running, hopping, and dancing.

ADDUCTOR GRACILIS.

A slender muscle passing down the inner side of the thigh.
(Fig. 92.)

Origin. — The inner edge of the ramus of pubes and ischium.

Insertion. — The inner tuberosity of the tibia, along with the
sartorius and the semitendinosus.

Structure. — A thin flat tendon above, slightly converging fibers,
a round tendon below.

Action. — The pull is directly inward and at a considerable angle
with the femur; it is also in a position to flex the knee. It can be
felt to act in all vigorous adduction of the hip and flexion of the
knee.

ADDUCTOR LONGUS.

This muscle lies just to the inner side of the pectineus (Fig. 92) .

Origin. — The front of the pubes, just below the crest.

Insertion. — The linea aspera in the middle third of the thigh.

Structure. — A thick triangular muscle, arising by a short tendon
and diverging fan wise to its wide insertion.

Action. — The pull of the adductor longus is similar to that of
the pectineus but it is plainly in a position to adduct more and
flex less than the latter muscle. Isolated action of the adductor
longus is a combination of flexion and adduction, but it does not
flex enough to lift the thigh over the other one while sitting, as
the pectineus does.

ADDUCTOR BREVIS.

A short muscle beneath the adductor longus (Fig. 98) .
Origin. — The front of the pubes, just below the longus.
Insertion. — The upper half of the linea aspera.
Structure. — A fan-shaped sheet similar to the longus but shorter.
Action. — The position of the brevis gives less power to flex the
hip and better angle of pull for adduction.

ADDUCTOR MAGNUS
ADDUCTOR MAGNUS.

171

One of the largest muscles of the body, situated beneath the
gracilis on the inner side of the thigh (Fig. 98) .

Fig. 98. — Front view of the adductors brevis and magnus. (Gerrish.)

Origin. — The front of the pubes, the tuberosity of the ischium,
and the whole length of the ramus connecting the two.

Insertion. — The whole length of the linea aspera and the inner
condyloid line.

172 MOVEMENTS OF THE HIP-JOINT

Structure. — The fibers from the pubes pass horizontally across
to the femur, much like those of the brevis; those from the ramus
lower on the linea aspera; those from the tuberosity of the ischium
go to the lower end of the condyloid line.

Action. — The upper half of the magnus works under the same
conditions as the longus and brevis except that the origin farther
back causes less tendency to flex the hip; the lowest fibers have
almost the same pull as the semitendinosus. Stimulation of the
whole muscle gives rise to adduction; the upper fibers give some
rotation outward ; the lower fibers, extension and rotation inward.

Loss of the adductors causes some difficulty in walking and run-
ning but is not nearly so serious as the loss of either the flexors,
extensors, or abductors. Those lacking the adductors swing the
limb forward and sideward in walking, pure flexion of the hip being
impossible, probably because of the abducting action of the tensors.

Vigorous action of the adductors is necessary in such exercises
as riding on horseback, climbing a rope or a tree, and a few similar
ones, but these are so unusual that one is apt to wonder what
should cause the development of so large a muscular mass as the
adductors when there is apparently so little work for them to do.
The explanation is probably the fact that most of these muscles
have some other action that is largely responsible for their develop-
ment; the longus used in flexion, the magnus in extension, and the
gracilis in flexion of the knee.

The ability of the adductor magnus to extend the hip is not
mentioned in text-books of anatomy nor by the investigators of
muscular action, but it is in a position to act on the hip exactly
like the semitendinosus and semimembranosus, with an origin close
alongside these muscles and the course of its lower fibers parallel
with them. Its lower attachment on the inner condyloid line should
give it the same power of extension as if it were attached to the
tibia, a short distance below. Study of the muscles during exten-
sion gives every evidence that the posterior fibers of the adductor
magnus takes part in this movement of the hip, and the size of the
muscle indicates important assistance in the work if it acts at all.

THE SIX OUTWARD ROTATORS.

The reader will recall that inward rotation of the arm is per-
formed incidentally by the large muscles having the larger duty
of swinging the arm, and that outward rotation is performed by a
special group of two muscles, the infraspinatus and teres minor.
It is interesting to find that in case of the hip we have a similar
arrangement, inward rotation being performed incidentally by the
great flexors and extensors along with their main work and out-

THE SIX OUTWARD ROTATORS 173

ward rotation by a special group, in this case of six in place of two ;
the pyriformis, obturator externus, obturator interims, gemellus
superior, gemellus inferior, quadratus femoris.

Origin. — The posterior portions of the pelvis.

Insertion. — The great trochanter of the femur.

Structure. — Fig. 96 shows five of these muscles; three of them
are named in the figure and the gemellus superior and inferior are
assistants of the obturator internus, the former above and the
latter below. The obturator externus is shown in Fig. 98.

Fig. 99. — Rotation in the hip-joints during walking. The amount of rotation is
indicated by the position of the stick.

Action. — The position of this group of six muscles indicates out-
ward rotation as their main action, and electric experiment gives
the same answer. It is true here, just as in case of the arm, that
forward movement of the limb through a right angle puts the group
in a position to produce abduction as well as rotation; it is easy to

174 MOVEMENTS OF THE HIP-JOINT

observe on a mounted skeleton that contraction of the outward
rotators while sitting will separate the knees.

If in walking and running the hips do not swing forward and
backward there is no rotation in the hip-joints, but usually the
hip goes forward as the foot goes forward, the amount of the swing
varying considerably in different individuals. Now a forward
swing of the hip as the limb swings forward will swing the toe in
unless there is outward rotation in the hip-joint. It follows that
in walking and running the limb must be rotated outward on the
side where the large muscles are doing little, calling for an extra
group to do it, while inward rotation must occur on the side where
the extensors and abductors are doing the main work of the move-
ment, and so they perform incidentally the slight work of rotating
the limb. In throwing and putting the shot and in batting and
serving the same is true; inward rotation is done with much more
power than the opposite.

QUESTIONS AND EXERCISES.

1. Pick out a right femur from the bones of a dismembered skeleton; point out
its great and small trochanters, its inner and outer condyles, its linea aspera and its
two condyloid lines.

2. Point out a sacrum, the ilium, the ischium, the pubes. Point out the place
of attachment of four muscles on each.

3. Measure on the mounted skeleton the breadth of the pelvis, the length of
the femur and the lengths of the gluteus medius, adductor magnus, semitendinosus,
rectus femoris and psoas.

4. When one stands on one foot and lifts the other knee to the level of the hip,
what muscles do the work on the limb that is lifted? On the limb on which the
subject stands? How is this changed if one holds a weight out sidewise at shoulder
level on the side of the knee that is lifted? How if one grasps instead a solid means
of support with that hand?

5. Give a list of five exercises for developing the flexors of the hip, arranged in
progressive order, proceeding from the easiest to the most difficult, basing the pro-
gression on amount of strength required rather than difficulty of coordination.

6. Stand with feet separated sidewise two foot lengths and hands at "Deck firm"
and see how far you can incline trunk forward by a movement in the hip-joints,
without bending either the knees or the trunk. Have several other persons try it
and estimate the number of degrees of inclination. Explain why one cannot bend
farther and why a slight flexion of the knees enables one to do so.

7. What acts as the lever in the forward inclination of the trunk just mentioned?
Where is the axis of movement? Where is the power arm? The weight arm?
Length of each? How does the angle of pull vary as one inclines forward? Why
does one move the hips backward in making the movement instead of merely moving
the head forward?

8. What advantage is there in swinging the hip forward as the foot goes forward
in walking? What disadvantage? Notice how people swing the arms while walk-
ing. Do the arms swing in the same direction as the hips or opposite? What is
the advantage of the swing of arms?

9. Study the movements of the hip-joints in rowing a boat. What movement
takes place in hip-joints as the oars are pushed forward? What muscles work to
perform this movement of the hips? When the pull is made upon the oars? Which
of the two sets of muscles do the most work in rowing?

10. What movements of the hips take place in climbing a ladder? How different
in climbing a stair? In climbing a rope? What muscles are used in the first two
cases and not in the third? In the third and not in the first two?

CHAPTER IX.

MOVEMENTS OF THE KNEE-JOINT.

The knee-joint is the largest and most complex joint in the
body and consists of two separate articulations between the tibia
and the femur. The two condyles of the femur rest upon the two
tuberosities of the tibia and fit into shallow depressions made by
two cartilages, the semilunar cartilages, which are joined to the
rather flat surface at the summit of the tibia. Near the median

Fig. 100. — The cartilages and ligaments within the capsule of the knee-joint,
viewed from above. (Gerrish.)

line of the knee, between these two articulations, are two strong
ligaments, the crucial ligaments, connecting the tibia and femur
and limiting the movements of the joint. Around the outside of
all these structures is the capsular ligament, reinforced by strong
bands of fibrous tissue on the inner and outer sides and the rear;
the patellar ligament, which connects the patella with the^tibia,
is'Jblendedwith the capsule on the front and strongly reinforces it
there. :

The knee acts much like a hinge joint, permitting only flexion
and extension excepting when it is flexed to 90 degrees or more;
this slackens the tension on the ligaments so as to permit 60 to 90

176 MOVEMENTS OF THE KNEE-JOINT

degrees of rotation of the tibia. One can easily notice the distinc-
tion between rotation in the hip and in the knee by observation of
his own limb while sitting in a chair. If the knee is held firmly
extended the toes can be turned in and out easily, and by feeling
the knee while this is going on it is easy to discover that there is
no rotation there, the whole thigh rotating upon its main axis with
the motion in the hip-joint; if the knee is flexed to 90 to 100 degrees
the toes can be turned in and out as before, but now the thigh does
not turn, the rotation taking place in the knee only. The possi-
bility of rotation of the knee in the flexed position is a convenience
in climbing a tree or rope, enabling one to use the leg and foot in
different positions; the absence of this rotation in the erect position
is a great convenience in maintaining a stable position on the feet.

Flexion and extension of the knee takes place by a gliding of
the condyles of the femur through the depressions on the head of the
tibia, different parts of the wheel-like surface of the condyle being
in contact with the tibia in different positions of the joint. In the
extended position the lower and more flattened part of the condyle
is in contact, giving a more stable support in the erect position;
in complete flexion it is the most posterior and most curved part
of the condyle and in semiflexion a portion between the two. The
semilunar cartilages are attached to the tibia so loosely that they
can adapt themselves to the changing shape the condyle presents
as various portions of it come into the depressions.

The patella is a flattened and rounded bone that is developed in
the tendon of the extensor muscles. Its anterior surface is rounded;
its posterior surface has a vertical ridge across it and is covered
with cartilage to lessen its friction as it glides over the front of the
femur. The movement is a combination of sliding and rolling.
The patella prevents the tendon of the extensors from drawing into
the groove between the condyles of the femur and thus improves
the leverage of these muscles on the knee-joint. The portion of the
extensor tendon below the patella, which is usually called the patellar
ligament, joins the tibia at a tubercle located at the lower edge of.
the front side of the inner tuberosity.

Flexion of the knee is possible through about 135 degrees, when
it is brought to a stop by contact of the tissues on the back of the
thigh and leg and by tension of the front of the capsular ligament
and the crucial ligaments. Overextension is usual to a slight extent
so that in the erect position the weight of the body tends to cause
further overextension; the crucial and posterior ligaments prevent
further movement and thus the extensor muscles are not needed
to hold the joint in extension, as long as one stands still and there
is nothing happening to disturb the balance.
L There are ten muscles acting on the knee-joint, all but four

MOVEMENTS OF THE KNEE-JOINT

111

of which have been described; three of the four will be described
in this chapter and the fourth, which acts mainly on the ankle-
joint, will be described in the next chapter.

Six flexors: semitendinosus, semimembranosus, biceps, sartorius,
adductor gracilis, gastrocnemius.

OUTER

BERO

STYLOID,

PROCESS

INNER TU-
BEROSITY

*NTERO-EXTER-_
NAL BORDER

ANTERO-INTER-
NAL BORDER

OUTER
MALLEOLU

INNER
ALLEOLUS

Fig. 101. — The right tibia and fibula, front view. (Gerrish.)

Four extensors: rectus femoris, vastus externus, vastus internus,
vastus intermedius.

Four rotators inward: semitendinosus, semimembranosus, sarto-
rius, adductor gracilis.
12

178 MOVEMENTS OF THE KNEE-JOINT

One rotator outward: biceps.

Among the flexors the semitendinosus and sartorius have the
best leverage, since they attach lowest on the tibia; next to them
are the gracilis and the biceps, with the semimembranosus nearest
the joint. The angle of pull is least at the start, when the knee is
in complete extension, and is best when it is flexed through a little
more than 90 degrees.

This group of muscles acts to lift the foot from the ground in
walking, running, hopping, climbing, jumping, and dancing, but
the resistance to be overcome is small, the weight of the leg and
foot being slight in comparison with the weight of the body, which
most of the muscles of the lower limb have to lift. It is surprising,
therefore, to find that when tested by a dynamometer the flexors
of the knee are nearly as strong as the extensors of the hip or of the
knee, in spite of the small amount of work they have to do in flex-
ing the joint. The explanation is to be found in the fact that the
three strongest of these flexors are also extensors of the hip, and
that they are able to use in flexing the knee all the power they
develop in the vigorous work they have in extending the hip.

VASTUS EXTERNUS.

A large muscle located half-way down the outer side of the thigh
and making the rounded eminence to be found there. It corre-
sponds closely to the outer head of the triceps of the arm (Fig. 93) .

Origin. — The outer surface of the femur just below the great
trochanter and the upper half of the linea aspera.

Insertion. — The outer half of the upper border of the patella.

Structure. — A small portion of the muscular fibers arise directly
from the femur near the trochanter; the greater part arise from a
tendon shaped much like a sheet of paper covering the outer sur-
face of the muscle for its upper two-thirds, with its posterior edge
attached to the linea aspera. The lower tendon is a flat sheet
attached to the upper border of the patella and serving as a tendon
of insertion for the three " vasti" muscles; it lies beneath the vastus
externus, and the muscle fibers pass obliquely downward and
inward from the upper tendon to join it.

Action. — The line of pull indicates plainly that the vastus externus
can extend the knee, and that it needs a companion from the inner
side to give a straight pull on the patella. The angle of pull is
nearly 90 degrees in the extended position and the presence of the
patella keeps it good in flexion as far as a right angle; the power
arm of the lever is about two inches in an average adult subject.
Electric stimulation of the vastus externus extends the knee power-

VASTUS INTERMEDIUS

179

fully and tends to pull the patella sidewise out of its groove;
paralysis of it makes a person liable to displacement of the patella
inward by action of the next muscle.

VASTUS INTERNUS.

This muscle, corresponding to the inner head of the triceps of
the arm, is located on the inner side of the thigh, somewhat lower
than the externus and partly covered
by the rectus and the sartorius.

Origin. — The whole length of the
linea aspera and the inner condyloid
line.

Insertion — The inner half of the
upper border of the patella.

Structure.— Similar to the exter-
nus. The tendon of origin is a flat
sheet arising from the linea aspera
and the tendon of insertion is the
same sheet to which the others
join.

Action. — The line of pull is just
like that of the externus except that
it is directed diagonally inward in-
stead of outward. Isolated action
causes inward displacement of the
patella and paralysis makes the
subject liable to outward displace-
ment.

VASTUS INTERMEDIUS.

A companion of the two preced-
ing, lying between them and beneath
the rectus femoris.

Origin. — The surface of the upper
two-thirds of the shaft of the femur.

Insertion. — The upper border of
the patella.

Structure. — The muscle fibers arise
directly from the bone and pass
downward and forward to join the deeper surface of the sheet
which serves as a tendon for the two preceding muscles.

Action. — The line of pull, like that of the rectus, is directly
upward on the patella, producing extension of the knee. The muscle

Fig. 102.— The three "vasti"
muscles. (Gerrish.)

180 MOVEMENTS OF THE KNEE-JOINT

lies too deep to be readily observed or stimulated, but its leverage
and its junction with the common tendon of the vastus externus
and vastus internus makes it reasonable to assume that its action
is the same.

The three muscles named "vastus," with the rectus femoris,
make up what is sometimes called the "quadriceps extensor" of
the knee; sometimes the internus and intermedins are considered
as one muscle, and then the group is called "triceps extensor," to
correspond to the like muscle of the arm. There are several simi-
larities; the external head is higher than the inner, the middle head
goes up past the joint above, and the inner head is the strongest;
the olecranon is somewhat like the patella, although the former
becomes in the adult a solid part of the ulna while the patella
remains detached from the tibia through life.

The extensors of the knee take part in all such exercises as walk-
ing, running, jumping, squatting, climbing, dancing, etc., where
the weight of the body tends to flex the knees; sometimes, as in
going up stairs or climbing a tree, they lift the weight of the body;
sometimes, as in going down the stairs or the tree, they perform a
"lengthening contraction" at each step, lowering the body without
fall or jar; sometimes, as in running and jumping, they do these
two things in alternation.

The extensors of the knee are very important factors in the per-
formance of the exercises mentioned in the last paragraph; they are
absolutely essential to running, jumping, climbing, and all move-
ments involving any considerable flexion of the knee from the
standing position, and their loss also causes serious trouble in
standing and walking. Anyone can observe upon himself that in
ordinary standing position the patella hangs loosely in the lax
front of the capsular ligament, so that it can be easily moved about
with the hand, and it is found that persons with the extensors of
the knee paralyzed can stand erect without difficulty, because of
the tendency of the weight of the body to overextend the knee.
Such persons can walk, providing they avoid flexing the hip far
enough to cause flexion of the knee by the weight of the leg and
foot. They do this by taking very short steps, which they lengthen
somewhat without danger by swinging the hip forward as far as
possible at each step, giving them a waddling and stiff gait. If
they try to hurry or swing the foot too far forward they fall. Chil-
dren with the extensors lost are apt to walk with the hands resting
on the knees, so as to keep them from flexing by the use of the
hands; this is laborious and leads to deformity of the trunk. What
is still worse, after the extensors have been lost for some time the
flexors shorten from lack of antagonism, keeping the knees flexed
and making walking impossible. This makes it necessary to wear

VASTUS INTERMEDIUS 181

an appliance that keeps the knee extended, and then the waddling
walk described above can be executed.

When the knee is flexed through 90 degrees or more it can be
rotated outward by contraction of the biceps and inward by the
semitendinosus, sartorius, and adductor gracilis, which attach to
the tibia together. This is easily observed by reference to one's

Fig. 103. — The extensors of the knee in action: R, rectus; E, vastus externus;
I, vastus internus.

own knee, while sitting with the feet on the floor and the knees
flexed to about 100 degrees. Place the hands on the sides of the
thigh near the knee, the thumbs on top and the fingers beneath;
notice the tendon of the biceps, plainly felt on the outer side, and
the tendons of the three muscles together on the inner side. Now
turn the toes forcibly outward and notice that the tendon of the
biceps springs into greater prominence and the inner group of

182

MOVEMENTS OF THE KNEE-JOltfT

tendons disappears under the finger-tips; reverse the rotation and
notice the reversal of the action of the muscles, as felt by the
finger-tips. This not only demonstrates the action of the muscles
employed in rotating the knee but also furnishes one of the best
illustrations of the inhibition of antagonists. It is easy to feel the
tendons of both the inner and outer hamstrings when the foot

Fig. 104. — The so-called tendinous action of the two-joint muscles of the thigh:
R, rectus femoris; P, psoas; Gl, gluteus maximus; H, hamstring; T, anterior tibial;
G, gastrocnemius. (Lombard.)

rests on the floor in normal position, but as soon as the tibia is
rotated in either direction the opposing tendon loses tension, in
spite of the fact that the rotation of the tibia would increase its
tension if the tone of the muscle were not diminished by nervous
influence.

We have noticed that the rectus femoris and the hamstring
muscles reach past two joints — the hip and knee; this fact has led

VASTUS INTERMEDIUS 183

to their being called "two-joint muscles" to distinguish them from
the "one-joint muscles," which cross but one joint. Besides the
actions we have studied thus far, and which may be called the
individual actions of these muscles, the two-joint muscles of the
thigh have a combined action due to their passing across the oppo-
site sides of the two joints and which has been called their "ten-
dinous action." When these two opposite sets of muscles are con-
tracted enough to have considerable tension they serve to connect
the two joints in the same way that a belt connects two pulleys,
so that if you move one of them, the other moves with it. For
example, if the hip is flexed by the psoas, iliacus, pectineus, and
tensor (Fig. 104, A), which are one-joint flexors of the hip, the belt-
like action of the two-joint muscles makes the knee flex also; this
is because flexion of the hip puts extra tension on the hamstring
group and lessens the tension of the rectus femoris, and the change
of tension of the two opposing groups flexes the knee. Now while
both joints are flexed, if the gluteus maximus, a one-joint extensor,
contracts and extends the hip (Fig. 104, B), the change of tension
on the belt will also extend the knee. These actions can be demon-
strated with a model like that shown in Fig. 104, illustrating the
general principle that the two-joint muscles of the thigh, when in
contraction, exert a belt-like action on the hip and knee such that
the two joints tend to take the same position and to move in the
same direction and to the same extent. It is evident that this
belt-like action will disappear when the two-joint muscles are
relaxed and will be most effective when they are in strong
contraction.

The two-joint muscles of the thigh are in strong contraction in
running, jumping, squatting, and similar exercises, and are there-
fore tending in these cases to make the hip and knee flex to the same
degree, thus keeping the trunk and tibia parallel, as in Fig. 105.
This will explain why everyone naturally keeps the trunk and tibia
parallel in such exercises, as all who have watched children at play
or gymnastics must have noticed, and why it is difficult for most
beginners to bend the knees and keep the trunk erect as in Fig. 106,
which is the form prescribed in Swedish gymnastics. To take the
position of Fig. 106 one must flex the knees to 90 degrees and the
hips to 45 degrees; how can this be done? The gluteus maximus
might stop the flexion of the hip at 45 degrees, but observation
shows that this muscle is idle. The vasti muscles, however, are in
strong contraction; the extent to which they lengthen will fix the
extent of flexion of the knee; to give the required position of the
trunk the hamstrings must shorten and the rectus lengthen slightly
as the knees flex. Since this is not an inherited coordination, like
running, it has to be learned by voluntary effort and practice.

184

MOVEMENTS OF THE KNEE-JOINT

The question naturally arises now whether the two-joint muscles
lose their individual action to flex and extend the hip and knee
when they act to tie these joints together and make their move-
ments correspond. The group on one side tends to extend the hip
and flex the knee while the opposite one tends to flex the hip and
extend the knee; when both contract with the same force it seems
as though they would neutralize each other's action and therefore
act passively, as a belt or connecting rod acts, to transfer to the

Fig. 105. — Natural position when knees are
bent while standing.

Fig. 106. — Position used in Swedish
gymnastics.

other joint any force applied at one of them. If, however, we
replace the cords in the model shown in Fig. 107 by rubber bands,
so as to bring to bear on the apparatus the natural tension of con-
tracting muscles, the two-joint muscles acting alone will extend
both joints; still more surprising, if we replace either one of the
two cords by a rubber band and leave the other cord in place, it
will extend both joints as before. We are thus confronted by the
problem, How can the hamstring-muscles, which are flexors of the
knee, cause extension of the knee? How can a cord tied across two

VASTUS INTERMEDIUS

185

joints give to a muscle that is primarily a flexor of a joint the
ability to extend it?

Dr. Lombard has explained this apparent contradiction by show-
ing that the two-joint muscles of the thigh have better leverage as
extensors than as flexors. The hamstring muscles have better
leverage at the hip and the rectus femoris at the knee; the pull of
the hamstring, Fig. 107, extends the hip in spite of the rectus because
its leverage on the hip is better; the added tension thus put on the
rectus causes it to extend the knee in spite of the direct pull of the
hamstring; the result is that the model comes to rest in the posi-
tion of complete extension of both joints. This advantage in
leverage consists both in length of power arm and angle of pull, in

Fig. 107. — Lombard's paradox: A, hamstring extending hip and flexing knee; B,
hamstring with aid of tendon action of rectus femoris, extending both joints.

erect standing position; when the hip and knee are flexed to a right
angle the angle of pull is practically the same in all four places, so
that the leverage in favor of extension is improving as we approach
the erect position.

The utility of having the leverage of these muscles favor exten-
sion is evident when we think of it. We have occasion constantly
to use the lower limbs in extension against the weight of the body
in standing, walking, running, climbing, dancing, and the like,
while we have to flex both joints at the same time against resistance
but rarely, as would be illustrated by lifting a weight attached to
the feet while hanging by the hands.

Suppose, however, we wish to make the movement just described ;
can the two-joint muscles of the thigh help to perform it? Not

186 MOVEMENTS OF THE KNEE-JOINT

when working together with their belt-like action, because their
leverage always favors extension; the rectus can never help to
flex the knee nor the hamstring to flex the hip, no matter what
linkage is used. Such a movement can be made best by the action
of the one-joint flexors of the hip and knee acting alone, for any
assistance of the two-joint muscles will do more harm than good.

QUESTIONS AND EXERCISES.

1. Select from a group of bones a right tibia and point out its inner and outer
tuberosities, its tubercle for the attachment of the patellar ligament, and the place
of attachment of five other muscles upon it.

2. Using an unmounted femur and tibia, demonstrate that the axis of the lower
limb passes through the tibia but not through the shaft of the femur; show how the
inequality of the length of the condyles of the femur causes this; show that the
knee is similar to the elbow in this respect.

3. Why is it more difficult to sit erect on the floor with feet extended forward than
on a bench or chair? Why does it help in this case to cross the legs, tailorwise?

4. Study the action of the knees in rowing with a sliding seat. What movement
of the knees is associated with the push on the oars? What muscles act to produce
this movement of the knees? What movement of the knees is associated with the
pull on the oars? What muscles do this? Test this out on the living body and
make sure.

5. Study the act of kicking a football. What muscles move the limb that kicks
the ball? Which way do they pull on the pelvis? What muscles act in the other
limb while the kick is being made? Do they pull the same way on the pelvis or help
to keep it in place? Which way does the player lean? Why?

6. What movement of the arm most closely resembles the rotation in the knee-
joint? In what respects are the two movements alike? In what respects are they
different? Amount of movement in each? Why cannot the foot be turned through
as many degrees as the hand by the combinations of rotations in the two joints?

7. Explain why one can turn the pedals of a bicycle forward more easily than
backward.

8. Is a football-player falling and having other pile on top of him more likely
to have his knee ligaments strained if he flexes his knees or keeps them straight?
Explain.

9. Standing on left foot with knees extended, place right foot on the floor behind
the left heel, the arch of the right touching the heel of the left and the lines of the
two feet at right angles; then place the right foot in front of left toe, arch of right at
toe of left, right toe pointing directly to left, lines of the two feet at right angles;
the right foot now points in exactly the opposite direction to the position it had
at first. Explain where this movement takes place and what muscles produce it.

10. Explain how the short head of the biceps can help to flex the hip, and give
an example of its action to assist the psoas and pectineus.

CHAPTER X.

MOVEMENTS OF THE FOOT.

The foot includes 26 bones so grouped as to form two arches,
transmitting the weight of the body to the ground at three points.
The bones are joined together by ligaments and the arches are

Fig. 108

MIDDLE CUNEIFORM

FIRST METATARSAL

Fig. 109
Figs. 108 and 109. — Bones of the foot. (Gray.)

kept from spreading by ligaments and muscles, forming an effi-
cient shock-absorbing mechanism to lessen the jar that would
otherwise result in walking, running, and jumping. The bones are
as follows :

Seven tarsal bones: astragalus, calcaneum, scaphoid or navicu-
lar, cuboid, and three cuneiform bones numbered from within
outward;

188

MOVEMENTS OF THE FOOT

Five metatarsal bones, numbered from within outward, and
Fourteen phalanges, three for each toe except the first, which has
two.

The principal arch passes transversely beneath the foot, as seen
in Fig. 108, the calcaneum forming its rear base and the minor
arch forming its front base. The minor arch is formed by the meta-
tarsal bones, the anterior ends of the first and fifth resting upon
the ground and the intervening three supported between them.
The weight of the body is transmitted through the tibia to the

ASTRAGALUS

FLEXOR
CHANNELS

TIBIALIS
POSTERIOR

SCAPHO-CUNEI- IB

FORM LIGAMENT WH|

TIBIALIS j-
ANTERIOR

PERONEUS
BREVIS

Fig. 110. — The plantar ligaments. (Gerrish.)

astragalus, which serves as the keystone of the main arch. So
great a weight pressing down on such flat arches tends to flatten
them out, requiring three strong supports to tie together the three
bases; one from the heel to the first metatarsal, one from the heel
to the fifth metatarsal, and one between the inner and outer meta-
tarsals. Of these three supports, acting like bow-strings to keep
the arches intact, one is ligamentous and the other two muscular.
The two calcaneocuboid or plantar ligaments, which are next to
the patellar ligaments the strongest in the body, bind the calcaneum
to the cuboid and the last three metatarsals beneath the outer side

MOVEMENTS OF THE FOOT 189

of the main arch, as seen in Fig. 110, so firmly that this side of the
foot acts almost as one solid piece. The inner side of the main
arch, which is better suited in some respects to climbing trees than
to walking and standing, is much more pliable, the bones being
linked together with smaller ligaments, leaving the support to be
supplied chiefly by contracting muscles.

The foot and toes, like the hand and fingers, have many minor
movements that do not concern us here, but there are four move-
ments of the foot concerned in bodily posture and exercise that we
need to study. These movements are as follows :

1. Elevation of the front of the foot and the toes, usually called
dorsal flexion or merely flexion;

2. Depression of the front of the foot and toes, usually called
extension or plantar flexion;

3. A rotation of the foot on a horizontal axis so as to turn the
sole inward, variously named adduction, inversion, supination, and
rotation inward;

4. The opposite of (3), turning the sole outward and called
abduction, eversion, pronation, or rotation outward.

These movements of the foot take place in four sets of joints:

1. The ankle-joint, which is a hinge joint formed by the articu-
lation of the tibia and fibula with the astragalus. Projecting pro-
cesses from above reach down past the joint, adding to its strength
and forming two rounded eminences, the inner and outer malleoli.
The ankle permits about 75 degrees of movement. Starting from
standing position, the knees can be flexed until the tibia inclines
forward 25 to 30 degrees with the foot flat on the floor; with further
movement the heel is lifted by the posterior ligaments of the ankle-
joint. The front of the foot can be depressed through about 45
degrees. The axis of the ankle-joint is parallel to that of the knee,
so that the flexed knee always points in the direction of the toes;
this is why in knee bending, as in Fig. 106, the knees separate at
the same angle as that between the feet in the standing position
from which the exercise is taken.

2. The tarsal joints, articulations between the seven tarsal bones.
There is some movement here in the same direction as that in the
ankle-joint, also rotation to turn the sole inward or outward, and
a slight lateral bending of the foot, so as to make either the inner
or outer border more concave. It is beyond our purpose to go into
all the details of movement in the tarsal joints.

3. The joints between the tarsal and the metatarsal bones, in
which the metatarsal bones can move slightly up and down and
very slightly in a lateral plane.

4. The joints of the toes, which are hinge joints, flexed when the
toes are bent downward and extended when they are raised.

190

MOVEMENTS OF THE FOOT

Eight muscles do the main part of the work in producing the
movements of the foot described above; the names of these muscles
and the distribution of the work is as follows:

Three lifting the front part of the foot: tibialis anterior, extensor
longus digitorum, extensor hallucis.

Three depressing the front part of the foot:
gastrocnemius, soleus, peroneus longus, assisted
slightly by the long and short flexors of the
toes.

Three turning the sole inward: tibialis an-
terior, gastrocnemius, soleus.

Two turning the sole outward: peroneus
longus, peroneus brevis.

Two bending the foot laterally: tibialis pos-
terior, peroneus brevis.

TIBIALIS ANTERIOR.

A slender muscle lying just outward from the
subcutaneous part of the tibia, on the front of
the leg. (Fig. 111.)

Origin. — The upper two-thirds of the outer
surface of the tibia and the corresponding por-
tion of the interosseous membrane that joins
the tibia and fibula.

Insertion. — The inner margins of the first
cuneiform bone and the first metatarsal.

Structure. — The muscle fibers arise directly
from the bone and are inserted obliquely into
the tendon of insertion, which is held down at
the ankle by a ring ligament.

Action. — If the tibialis anterior were to pull
straight from origin to insertion it would raise
the foot with very favorable leverage; binding
the tendon down at the ankle makes it pull at
a smaller angle, lessening the power and in-
creasing the speed of movement. The insertion
is so near the inner margin that it will lift the
inner side most strongly, tending to turn the
sole in.

Isolated action of the tibialis anterior causes lifting of the fore-
part of the foot, the motion taking place in both the ankle and
tarsal joints; the inner side of the main arch of the foot is straight-
ened out; the sole is turned inward; the last joint of the great toe
is flexed or depressed, because the lifting of the foot puts extra
tension on the flexor muscles, beneath the foot. (See Fig. 112.)

Fig. 111. — Muscles
of right leg, front view.
(Gerrish.)

EXTENSOR PROPRIUS HALLUCIS 191

EXTENSOR LONGUS DIGITORUM.

Similar to the preceding, and just exterior to it (Fig. 111).

Origin. — The outer tuberosity of the tibia, the front of the fibula,
and the front side of the interosseous membrane.

Insertion. — Top of the bones of the four outer toes.

Structure. — A penniform muscle with a long tendon beginning at
the middle of the leg. As it passes under the ring ligament of the
anlde the tendon divides into four that pass to the toes.

Action. — The pull is like that of the tibialis except that it acts
on the outer side of the foot, and therefore will tend to turn the
sole out rather than inv Isolated action lifts the outer side of the
foot with little effect on the inner side.

Fig. 112. — Isolated action of the tibialis anterior: A, insertion of the muscle;
B, its tendon at the anlde; C, C, the stimulating electrodes, applied to the skin
over the muscle. (Duchenne.)

EXTENSOR PROPRIUS HALLUCIS.

A smaller muscle lying beneath the last two and between them
(Fig. 111).

Origin. — The front side of the fibula and of the interosseous
membrane, at the middle half of the leg.

Insertion. — The top of the last phalanx of the great toe.

Structure/ — Like the preceding.

Action. — Strong extension of the great toe, feeble action on the
tarsal joints, no effect on the ankle.

The three muscles just described, usually called the flexors of
the foot, are brought into action in walking, running, and all simi-
lar movements to raise the toes and front of the foot and prevent

192 MOVEMENTS OF THE FOOT

their striking or scraping on the ground. The tibialis and the
extensor longus are both needed to give even elevation of the foot;
the extensor of the great toe is included in the coordination, as
anyone can notice by observing this movement of his own foot, to
counteract the depression of the toe caused by the action of the
tibialis, as shown in Fig. 112. People who have lost the use of this
group of muscles scrape the foot on the ground at each step in
walking.

GASTROCNEMIUS.

The large muscle that gives the rounded form to the calf of the
leg near the knee (Fig. 111).

Origin. — By two tendons from the back sides of the condyles of
the femur.

Insertion. — The back side of the calcaneum.

Structure. — The upper tendons are flattened; the lower (tendon
of Achilles) is very large and has a cross-section like a letter T,
with the upright part between the right and left halves of the
muscle and the crossbar on its posterior surface ; the fibers from the
two upper tendons pass diagonally downward to join the sides of
the tendon of Achilles at various levels.

Action. — The upper attachments are too near the axis of the
knee to give good leverage, but the wide movement of the con-
dyles of the femur during flexion and extension of the knee will
vary the tension on the gastrocnemius greatly. Its pull on the
ankle is with a long lever arm and a large angle. Lifting the cal-
caneum, it will depress the front of the foot; since the plantar
ligaments connect the calcaneum with the outer margin of the foot
only, its entire force will be exerted there.

Isolated action of the gastrocnemius extends first the ankle- and
then the tarsal joints; the latter joints being somewhat oblique,
the last part of the movement depresses the outer margin of the
foot more than the inner, turning the sole somewhat inward. If,
while the muscle is being stimulated, the observer pushes strongly
upward on the sole of the foot, the outer margin is found to be
depressed with great power, while the inner margin can be easily
lifted and the arch straightened out in spite of the contraction.
Stimulation of the gastrocnemius while the subject is standing at
rest on his feet causes the heels to be lifted and the weight to be
sustained on the outer margin of the foot.

SOLEUS.

An associate of the gastrocnemius, lying beneath it on the back
of the leg.

Fig. 113.— Muscles of the right leg, seen from the right side. (Gerrish )
13

194 MOVEMENTS OF THE FOOT

Origin.- — The upper part of the posterior surfaces of the tibia,
fibula, and interosseous membrane.

Insertion. — By the tendon of Achilles into the calcaneum.

Structure. — Penniform sheets.

Action. — The soleus has the same pull and leverage on the foot
as the gastrocnemius, but lacks any connection with the femur.

The gastrocnemius and soleus, sometimes called the triceps of
the leg, act together in all such movements as standing, walking,
running, jumping, dancing, climbing, etc., where the weight of the
body is supported on the feet and lifted by them. When the knee
is flexed to 90 degrees or more the gastrocnemius seems to be left
out of the coordination, leaving the work of extending the foot to
the soleus; in this position the heads of the former are so low that
it cannot pull effectively.

In the frog the tibialis anterior reaches above the knee and is
attached to the front of the femur, forming with the gastrocnemius
a pair of two-joint muscles whose belt-like action tends to make the
knee and ankle work in unison, like the hip and knee. This links
the whole lower limb into a series of levers for extension of all the
joints at once, with all the one-joint extensors as well as the two-
joint extensors applying their force to the whole system. The
result is a remarkable mechanism for jumping. In man the attach-
ment of the tibialis below the knee leaves a gap in the system, but
the gastrocnemius acts in much the same way alone. The attach-
ment of this muscle to the condyles of the femur, causing increased
tension upon it when the knee is extended, makes it possible to
use any surplus of force in the thigh muscles to help lift the heel.

The leverage of the triceps of the leg in lifting the heel has been
a puzzling question with anatomists, some claiming that it is a
lever of the first class with the axis at the ankle and others that it
is a lever of the second class with the axis at the toes. The confu-
sion is due to the fact of the machine's lifting itself, the situation
being too complex to be any form of simple lever. One assump-
tion in simple levers is that the fulcrum- is stationary; this is vio-
lated if we call it a first-class lever. Another is that the two forces
acting on the lever are independent; if we call it a. second-class
lever we have the muscle pulling up on the lever and down on the
weight to be lifted. The force of contraction of the muscles needed
to lift a person of known weight can be computed by assuming it
to be a lever of either class, but if we call it second class we must
add in the reaction of the pull and this involves a geometrical
series.

PERONEUS LONGUS.

This muscle is remarkable for its great power in proportion to
its size and for the long and tortuous course of its tendon of inser-

PERONEUS LONGUS

195

tion. It is situated along the fibula on the outer side of the leg,
just beneath the skin.

Origin. — The outer tuberosity of the tibia and the upper two-
thirds of the outer surface of the fibula.

Insertion. — The outer margins and lower surfaces of the first
cuneiform bone and first metatarsal.

Structure. — The fibers are short and arise directly from the fibula,
one of the best examples of simple penniform arrangement; the
tendon of insertion passes down behind the outer malleolus, turns
forward around its lower end at an angle of about 60 degrees,
passes forward along the outer margin of the foot to the groove in

Fig. 114.

-The extensors of the ankle in action: G, gastrocnemius; S, soieus;
P, peroneus longus.

the cuboid bone, where it makes another turn of about 100 degrees,
then diagonally forward and across the sole of the foot to the place
of insertion at the base of the great toe.

Action. — A cord looped around the base of the first metatarsal,
drawn through the groove in the cuboid and around the outer
malleolus and then held vertically beside the fibula, indicates the
direction of pull. The mounted skeleton does not Usually allow
movement here so as to permit useful experiment. The direction
of pull suggests that the peroneus will prevent the minor arch from
spreading; whether it will move the tarsal or ankle-joints can be

196 MOVEMENTS OF THE FOOT

little more than conjectured, so far as one can judge from the course
of the tendon.

Isolated action of the peroneus longus first depresses the great
toe and draws it outward, increasing the curvature of the principal
arch of the foot on the inner side; stronger action turns the sole
outward; finally it extends the ankle slightly. All these movements
are made with little force unless the ankle is forcibly extended by
the tendon of Achilles, since the peroneus uses the cuboid bone as a
pulley and its force is lost unless the pulley is held firm. Duchenne
reports that pulling upon the tendon of the peroneus in a fresh
cadaver produces exactly the same movements of the foot as elec-
tric stimulation, and that loss of the muscle also verifies it; he
points out that electric stimulation of the gastrocnemius in a nor-
mal subject gives the same movement of the foot as voluntary
attempt to depress the toes when the peroneus is lacking.

The work of Duchenne on the gastrocnemius and the peroneus
longus is probably the most important of all his researches on the
action of muscles, partly because of the great importance of these
two muscles in the posture and movement of the body, and partly
because the problems here are not problems of coordination but
problems of mechanical nature which his methods are especially
calculated to solve. Attacking these problems relating to the
support of the body on the foot and the causes of deformities of the
foot by three separate methods, he explains every detail so fully
and clearly that, although published in 1867, his chapters on the
movements of the foot are still the best by far of anything we have
on the subject.

The gastrocnemius, soleus, and peroneus longus work together
in all bodily exercises in which the weight is borne by the feet,
and their combined action is necessary to the normal working of
the foot; the loss of the triceps of the leg causes inability to extend
the ankle and the loss of the peroneus longus causes a flat foot.

TIBIALIS POSTERIOR.

Situated deep beneath the triceps on the back of the leg.

Origin. — The upper half of the posterior surface of the inter-
osseus membrane and the adjacent parts of the tibia and fibula.

Insertion. — The lower and inner surfaces of the scaphoid and the
first cuneiform bone, with offshoots to adjacent bones.

Structure. — Simple penniform; the tendon turns through 90
degrees around the inner malleolus.

Action. — The pull is almost directly backward on the scaphoid
and cuneiform bones, which can do little to flex or extend the ankle;
it ought to help support the weaker side of the arch, preventing
the weight of the body from crowding the astragalus down between
the calcaneum and scaphoid; it does not reach the first metatarsal

PERONEUS BREVIS

197

and therefore cannot act as an effec-
tive support for the arch.

Isolated action of the tibialis pos-
terior, according to Duchenne, bends
the foot laterally, making the inner
margin more concave, increases the
curvature of the arch, and has little
or no effect on the ankle.

PERONEUS BREVIS.

A small associate of the longus
(Fig. 115).

Origin.— The lower two-thirds of
the outer surface of the fibula.

Insertion. — The lower side of the
base of the fifth metatarsal.

Structure. — Fibers arranged like the
longus, similar turn around the outer
malleolus, direction forward and
downward to the insertion.

Action. — From the direction of pull
one would judge that the peroneus
brevis will lift the outer margin of
the foot and bend it laterally so as
to make the outer edge more con-
cave. In spite of the assertion of
most anatomists that both the tibialis
posterior and the peroneus brevis
extend the ankle, Duchenne says
that they neither flex nor extend it,
but tend to hold it in the normal
position between the two. On a
mechanical question like this his
experiments by electric stimulation
and traction upon the severed ten-
dons should give the most reliable
conclusions.

The muscles shown in Figs. 116
and 117, with a few others beneath
them, especially those toward the
inner side, help to support the arch
of the foot when the weight of the
body is placed upon it. Their

Fig. 115. — The tibialis posterior and peroneus
brevis of right foot. (Gerrish.)

198

MOVEMENTS OF THE FOOT

primary duty, however, is to move the toes and they are not able
alone to keep the arch from flattening out under the body weight
if the triceps of the leg or the peroneus longus or both of them
are lost.

Fig. 116 Fig. 117

Figs. 116 and 117. — The first and second layers of the muscles of the sole.

(Gerrish.)

DEFECTS OF THE FOOT.

Deformities of the foot are sometimes produced by paralysis or
atrophy of certain muscles, as a result of which the remaining
muscles pull the joints into abnormal positions; a similar deformity
is sometimes caused by abnormal shortening of certain muscles
which is called contracture. The most common of these deformities
are as follows:

DEFECTS OF THE FOOT 199

1. Paralysis of the gastrocnemius and soleus with the resulting
shortening of the tibialis anterior and extensor longus give the
deformity called calcaneus, where the forefoot is kept up and the
patient walks on the heel.

2. Contracture of the gastrocnemius and soleus produces the
form of defect called equinus, the weight being supported on the
toes and the heel unable to touch the ground.

3. Contracture of the tibialis anterior and posterior or loss of the
peroneus longus causes varus, in which the sole is turned in.

4. Contracture of the peroneus longus causes valgus, in which
the sole is turned out and the patient walks on the inner margin of
the foot.

5. Weakness of the muscles and ligaments supporting the arches
of the foot give rise to flat-foot, which usually begins with flattening
of the main arch and later includes valgus; the order of events may
be the opposite of this, a habit of walking on the inner margin of
the foot leading to flat-foot because it throws the weight on the
weaker side of the arch. This defect of the foot is very common
and is becoming more so, giving it special importance.

The main cause of flat-foot is muscular weakness; inability of
the muscles to hold the foot in proper position against the weight
of the body. This may result from disease but more often from
lack of development through exercise. Flat-foot most often occurs
in people who have gained weight rapidly, especially after an ill-
ness that has kept the muscles of the feet idle for some time, and
in people who stand upon the feet many hours each day but do
not move about enough to give the best kind of exercise for devel-
oping the feet. Shoes of wrong shape, too tight, with too high
heels, and with heels worn off on the inside all add to the tendency.

Tight shoes probably cause more of the trouble than any other
one thing because a tight shoe prevents muscular development;
it does this both by restricting the circulation of blood and lymph
and by preventing exercise of the muscles. A tight shoe, if it has
correct shape, may be a help if used rightly; for example, an athlete
running a race or a clerk standing for a long period on a hard floor
may have the feet supported and prevented from flattening by
tight shoes, but their use is in an emergency; the athlete and the
clerk must both discard them for looser ones while developing the
feet through exercise.

Walking with the toes turned out at an angle of 45 degrees or
more is conducive to flat-foot, since in this position, shown in
Fig. 119, the entire weight is borne by the inner and outer margins
of the foot in alternation, while it is sustained more easily if borne
by both sides at the same time, as in Fig. 118.

Flat-foot is sometimes caused by rupture or stretching of the

200

MOVEMENTS OF THE FOOT

plantar ligaments by alighting too heavily on too hard a surface,
as in the case of an athlete accidentally alighting on a hard spot
from a pole vault or a broad jump.

The chief preventive measure for warding off flat-foot is muscu-
lar development by suitable exercise of the feet. Those who have
in childhood played active games and who have kept up a moderate
practice of outdoor sports later are not apt to suffer from flat-
foot, unless from some excess or accident.

Fig. 118 Fig. 119

Figs. 118 and 119. — Fig. 118 correct and Fig. 119 incorrect position of the feet in

walking. (Ethel Perrin.)

Those who have acquired flat-foot should be treated by a
specialist. The most successful form of treatment includes the use
of some artificial support for the arch while doing things that would
strain it, together with exercises to develop necessary strength in
the muscles that lack it. Without the latter there can be no per-
manent cure, for the artificial support, like any other form of

FUNDAMENTAL MOVEMENTS OF THE LOWER LIMB 201

crutch, can do no more than bear the weight temporarily while a
cure is being effected. Circumduction of the foot while it is not
bearing any weight is one of the best exercises for weak feet, and
walking on the outer margin of the foot is good when the plantar
ligaments are intact.

One of the surest ways to detect flat-foot in early stages is to
observe the foot from the rear while the subject is standing. In
the normal foot the tendon of Achilles is straight, while in flat-
foot it bends at the level of the ankle, the lower end bending out-
ward and the inner malleolus being too prominent. This position
is sometimes taken through habit or because the inner side of the
heel of the shoe is worn off, but this habitual position is so apt to
lead to flat-foot that it is entirely proper to consider the position
an indication of the defect. A weakness of the peroneus longus and
other muscles supporting the inner side of the main arch of the foot
causes this turn of the sole outward because the upward thrust of
the ground is all met at the outer margin of the foot and the down-
ward thrust of the weight of the body at the ankle, which is at its
middle; the result is great tension on the inner ligaments of the
ankle, eventually elongating them and turning the foot over.

Flat-foot is sometimes very painful, because of the excessive
pressure caused at certain points of contact of the bones and by
pressure on nerves and bloodvessels lying beneath the arch of the
foot.

FUNDAMENTAL MOVEMENTS OP THE LOWER LIMB.

Walking, running, and jumping are inherited coordinations,
sometimes modified for gymnastic, military, and athletic purposes.
The main work of these movements being performed by the lower
limb as a whole, we are in a position for the first time to study
and analyze them.

Walking. — The photographic method enables us to observe exactly
what movements occur and when they occur in such an exercise as
walking, much more easily and accurately than we can by observa-
tion of the moving body. The sensitive film can record for our study
several positions in regular intervals of time during one complete
cycle of walking, beginning when one foot strikes the ground.

The photograph shows simultaneous extension of the hip, knee
and ankle on the supporting side for the first stage of the movement,
which brings into action all the one-joint and two-joint extensors
of the whole lower limb except the gluteus maximus. At the same
time the other gluteus medius and minimus are in action to keep the
hip from dropping down and to rotate the pelvis inward on the

202 MOVEMENTS OF THE FOOT

head of the femur. A slight flexion of the knee and ankle seen just
as soon as the weight is transferred to the other foot is found, by a
trial the reader can make upon himself, to be caused by the effect of
the weight of the body at the instant the foot is placed on the ground,
the extensors of the knee and ankle not being fully contracted as
yet and thus permitting a slight flexion that avoids a jar and also
avoids an immediate and sudden lifting of the whole body that
would otherwise result from the slanting position of the left limb.
The hip is fully extended when the body is exactly above the foot,
and since the iliofemoral band will prevent further extension during
the next interval the joint must be stationary, and the same is true
of the following positions, but the extensors "must be working and
bearing the weight just the same. Test will also show the rectus
femoris working during this phase of the step, although it is some-
times a flexor of the hip.

After the transfer of the weight we have simultaneous flexion of
hip, knee and ankle in the free limb, requiring much less force than
the preceding stage. The rectus femoris can be felt to cease contrac-
tion at this time, but the sartorius, pectineus, adductor longus and
tensor contract, and probably also the psoas and iliacus. The
hamstring muscles continue in contraction and, being relieved of the
weight of the body and the extensors of the knee relaxing, they
quickly flex the knee. At a certain stage the knee is seen to be
flexed to almost a right angle; after that the hamstring muscles
relax and the knee swings passively into almost complete extension
just before the foot comes to the ground again. The ankle, which
is fully extended in the middle position, the foot giving a final push
just before leaving the ground, flexes in a passive manner while it is
swinging forward, and later it is flexed actively by the anterior tibial
group to keep it from scraping the ground. During the last half
of the cycle the limb is being rotated outward by the six small
rotators. Notice that the arm is swung forward as the limb moves
backward.

The extent of each of these movements is increased as the step
is lengthened. Practice in observation will enable us to notice and
analyze the peculiarities of walk of individuals, which are due in
part to muscular peculiarities and in part to habits of coordination.
Some strike the foot too hard on the ground by contracting the
vastus group too strongly at the time the knee and ankle should
yield to the weight of the body; some wear their shoes through on
the inner side by failing to use the adductors of the free limb suffi-
ciently while others drop the free hip at each step by failing to
use the abductors of the supporting hip sufficiently; many children
turn the toes in on one or both sides while walking by failing to
use the outward rotators as the limb swings forward.

FUNDAMENTAL MOVEMENTS OF THE LOWER LIMB 203

Marching. — Marching is a modification of walking in which the
individual is taught to avoid some of his peculiarities of gait by
standing erect and keeping time with the other members of the com-
pany or class; one learns by such practice 'to walk at any given
rhythm and at the same time to vary his stride to any length used
by his associates. To emphasize the development of the extensors
of the foot, marching is sometimes done with extra effort to extend
just as it comes to the ground, making the toes strike first. For
development of the thigh muscles and for purposes of display,
marching has been modified in several ways, one of the most extreme
forms having the knee raised as high as the hip and then the knee
extended forward. "Bent knee" marching, described at length by
Regnault and Raoul, is a march with long strides and with the knees
in deeper flexion than in the usual forms; it is advocated for its
economy of force and speed.

Running. — Running differs from walking in a few minor details.
The most important of these is the spring from the ground, the body
being unsupported for a part of each stride. One foot is on the
ground for about one-third of the time and the other foot for the
same, leaving the body unsupported for about one-third of the time;
this will vary with the length of the stride. As the weight is borne
by the front of the foot alone, the heel not touching, the flexion
of the knee when the foot first strikes is not so much needed to
prevent jar as in walking. The greater speed of the run makes it
possible to leave the ground at each step and still have but little
more up-and-down oscillation of the body than in walking. Notice
that the hip and knee are flexed considerably just as the body is
over the foot and the limb inclines forward as it extends, making
the vertical oscillation very slight.

Jumping. — Jumping does not differ essentially from running, the
spring from the foot being made in the same manner, only in jump-
ing we do not repeat the movement but alight on both feet. In the
running jump the spring is made as in running, while in the standing
jump the spring is from both feet. In both cases we get the most
efficient use of the mechanism of the lower limb, which, as we have
seen is so constructed that all the one-joint and two-joint extensors
can bring their forces to bear on the system of levers at once.
As soon as the feet leave the ground in the jump the limbs flex by
a sort of recoil from the violent extension, the extensors of the
knee relaxing first and allowing the hamstring muscles to flex the
knees; just before alighting the knees are again nearly extended,
to yield again to the weight of the body when the feet strike. In
alighting as well as in the spring the whole mechanism of the limb
comes into action to support the weight and at the same time to
prevent injury from its being stopped too suddenly in its flight.

204 MOVEMENTS OF THE FOOT

In the high jump, as well as in the broad jump, the best record
can be made from a run, because this carries one quickly over the
bar, so that one can clear it without remaining above it so long.

QUESTIONS AND EXERCISES.

1. Point out the two arches of the foot, the tarsal bones, the metatarsal bones, the
position of the plantar ligaments.

2. Explain how the gluteus maximus can help to extend the ankle.

3. A man alighting from a high jump strikes a hard spot on the mat with the ball
of the great toe. What muscle is apt to be strained? Explain how this strain will
be felt high up on the outside of the leg. Explain how he can also have a sore spot
near the top of the instep, caused by the same accident.

4. Explain how contracture of the peroneus longus and weakness of the same
muscle both result in walking on the inner margin of the foot.

5. Why are those who walk or run flat-footed more likely to sprain their ankles
than those who go on the toes?

6. A man weighing 100 pounds stands on a table with his heels projecting slightly
over the edge, so that your fingers can be placed under them. If you lift up on his
heels, his feet act as second-class levers, and if his ankle-joints are one-quarter of
the distance from heel to toes it will require a lift of but 75 pounds to raise his heels
from the table. Under the same conditions he must contract his triceps or legs with
a force of 300 pounds to accomplish the same movement himself. Explain.

7. How far can you flex your knees while standing and still keep your heels on the
floor? Why cannot one flex them farther without lifting the heels? How account
for the difference found between individuals in this respect?

8. Explain the advantages and disadvantages of high-heeled shoes.

9. It is a favorite stunt among boys to jump and strike the feet together two or
three times before striking the ground again. What muscles perform this movement
and how is it done?

10. Write in a column the names of all the muscles of the lower limbs. Write
in a parallel column several inches away a list of all the movements of all the joints.
Draw a line from each muscle to all the movements it takes part in, making a complete
chart of the actions and the muscles.

PART IV.

THE TRUNK.

CHAPTER XL
MOVEMENTS OF THE SPINAL COLUMN.

The bony axis of the trunk, called the spinal column, consists of
33 vertebrae; 24 of these are joined to form a flexible column. Seven
vertebrae are in the neck and are called cervical vertebrae; 12 are
in the region of the chest and are called thoracic or dorsal verte-
brae; 5 are in the lumbar region; 5 are fused together to form
the sacrum, the rear portion of the pelvis; the lower 4 are only
partially developed and form the coccyx. The spinal column is
flexible above the sacrum, upon which the flexible portion rests.
Each vertebra bears the weight of all parts of the body above it,
and since the lower ones have to bear much more weight than the
upper ones the former are much the larger. The flexibility of the
column makes it possible to balance the weight upon the vertebrae
in sitting and standing.

Each vertebra has a dozen or more parts or points of interest to
be observed. The body is the largest portion and the most impor-
tant, since the weight is transmitted through it; passing to the rear
are the two pedicles, then the two laminae, the five enclosing the
spinal foramen. A spinous process extends to the rear and a trans-
verse process from each side; four articular processes, two above
and two below, have articulations with the next vertebrae; beneath
each pedicle is an intervertebral notch, leaving a place for nerves
to leave the spinal cord. Besides these points, to be found on all
vertebrae, the thoracic vertebrae also have four articular processes
or facets for the attachment of the ribs.

The skeleton of the chest or thorax includes the sternum and
twelve pairs of ribs, a pair for each thoracic vertebra. The ten
upper ribs are attached to the sternum by the costal cartilages, the
lower two being attached only to the vertebrae.

The vertebrae are separated by elastic disks of cartilage called

206

MOVEMENTS OF THE SPINAL COLUMN

the intervertebral disks, which are firmly joined to the bodies of
the vertebrae and which permit movement of the column because

DEMIFACET FOR
HEAD OF RIB.

SUPERIOR ARTICU-
LAR PROCESS.

FACET FOR TUBER-
CLE OF RIB.

Fig. 120. — A thoracic vertebra seen from above. (Gerrish.)

Fig. 121. — The ligament of the neck. (Gerrish.)

of their elasticity. Besides the union through the disks the verte-
brae are joined by ligaments; the bodies by an anterior and a pos-

MOVEMENTS OF THE SPINAL COLUMN 207

terior common ligament extending from the skull to the sacrum
along their front and rear surfaces and by short lateral ligaments
joining the bodies of adjacent vertebrae; the laminae are joined by
the subflava ligaments, which enclose the spinal canal, and the
spinous processes by the interspinous ligaments. In the cervical
region these processes are short and the interspinous ligaments are
replaced by a single strong elastic ligament, the ligamentum nuchae
or ligament of the neck. In quadrupeds this ligament has to sup-
port the weight of the head and is much larger than in man.

The normal spinal column is approximately straight when viewed
from the front or rear; it has a slight curve to right in the thoracic
region, supposed by some to be due to the pressure of the aorta
and by others to the pull of the right trapezius and rhomboid,
which are used more than the muscles of the left side by right-
handed individuals. This deviation from a straight line is too slight
to be observed in the normal living subject.

When the spinal column is viewed from the side it presents four
so-called normal curves: cervical and lumbar curves, concave to
the rear, and thoracic and sacral curves, convex to the rear. These
curves merge gradually into one another, the only approach to an
angle being where the last lumbar vertebra joins the sacrum; the
sharp bend here is due to the fact that the top of the sacrum slants
forward about 45 degrees with the horizontal, giving the sacral
angle (Fig. 122).

The thoracic curve exists before birth, and is chiefly due to the
shape of the bodies of the vertebrae, which in this region are slightly
thinner at their front edges (see Fig. 122). The cervical and lum-
bar curves are not present in the young child, which has a single
curve convex to rear through the entire extent of the spine. The
cervical curve is formed by the action of the child's muscles when
he begins to sit up and hold his head erect, and later to a more
marked extent when he raises his head to look forward while creep-
ing. The lumbar curve is formed in a similar way when he first
stands on his feet. Up to this time the child's hip-joints are kept
flexed to a considerable extent; even when he lies on his back he
seldom extends the hips fully. When he begins to stand on his
feet the iliofemoral band is put on a stretch for the first time,
holding the pelvis tilted forward; to rise to erect position he has to
fully extend the spine in the lumbar region, which gives the normal
curve. The cervical and lumbar curves are due to the shape of the
disks rather than to the shape of the vertebrae.

Movements of the spinal column take place by compression and
traction of the elastic disks and by gliding of the articular surfaces
upon each other. Bending the trunk forward, bringing the face
toward the pubes, is called flexion; the opposite movement as far

208

MOVEMENTS OF THE SPINAL COLUMN

as the normal position is called extension; backward movement
beyond a normal posture is overextension; bending sidewise is
called lateral flexion and rotation on a vertical axis is called rota-
tion or torsion.

CERVICAL

VERTEBR/E

THORACIC
VERTEBRA

LUMBAR
VERTEBR/E

s«<_

Fig. 122. — The spinal column. (Gerrish.)

Flexion takes place in all regions of the spine but is most free in
the lumbar region. The lumbar and cervical curves can usually
be obliterated by voluntary flexion in young subjects and the
thoracic curve considerably increased. The shape of the articular
processes in the lumbar region is calculated to permit flexion and
extension while preventing other movements. The total amount

MOVEMENTS OF THE SPINAL COLUMN 209

of flexion possible in the spine is apt to be overestimated because
the movements in the hip and in the joint between the head and
the spine are easily mistaken through superficial observation for
actual flexion of the trunk.

Extension is free in normal subjects; overextension is possible
to a slight extent in the cervical and thoracic regions and to a
much greater extent in the lumbar region and in the lower two
thoracic segments. The fully overextended spine, as Dr. Lovett
observed, is shaped like a hockey stick, with the chief bend at the
lower end.

Lateral flexion is possible to a slight degree at all levels but is
most free at the junction of the thoracic and lumbar regions. The
ribs prevent much lateral movement in the region of the chest and
the interlocking processes prevent it in the lumbar region. Con-
siderable lateral movement is possible in the neck but is less
important.

Rotation is most free in the upper parts of the spine and less
free as we pass downward, being prevented in the lumbar region
by the processes. The shape of the articular processes permits
rotation above, the limitation in the chest region being due to the
ribs. Rotation is said to be to right or left according to the way
it would turn the face.

Lateral flexion and rotation of the spine are usually described
separately by authors on anatomy although, as Dr. Lovett has
pointed out, the two movements never occur separately. To state
the same thing in other words, lateral flexion of the trunk always
involves rotation at the same time, and rotation of the trunk
always involves lateral flexion. This fact is illustrated by Fig. 123,
which snows a normal subject sitting on a slanting seat; the seat
compels her to flex the trunk sidewise to keep her balance; the
cardboard pointers, glued to the skin, indicate the direction of the
spinous processes and show a rotation of the vertebrae, especially
marked in the lower thoracic region, where most of the lateral
flexion occurs. The subject is bending forward so as to simplify
the conditions, the lumbar curve acting to complicate matters
unless removed by flexion forward.

The presence of rotation, such as this figure shows, accompany-
ing all lateral flexion of the trunk, is explained by an unfamiliar
law of mechanics to the effect that if a flexible rod is bent first
in one plane and then in another it always rotates on its longi-
tudinal axis at the same time. To see why this is true think of the
conditions existing in the case shown above. When the subject
bends forward, giving a condition always present in the thoracic
region, it puts a tension on the ligaments at the rear (subflava and
interspinous) that makes them resist lateral flexion more than
14

210 MOVEMENTS OF THE SPINAL COLUMN

usual, while the weight, bearing down on the front edges of the
bodies, aids in the lateral bending. The result is that the bodies
of the vertebrae go farther away from the vertical than the pro-
cesses during lateral flexion, and this is the rotation shown by
the pointers. The general principle, which is self-evident and
which helps one to remember in which direction the rotation will
be, is that the concave side of the normal curve, being under press-
ure, turns to the convex side of the lateral curve. It follows that

Fig. 123. — The rotation of the vertebra that accompanies lateral flexion of the
trunk. The pointers attached to the back show the direction of the spinous pro-
cesses. (Lovett.)

in the thoracic region a lateral bend rotates the spinous processes
to the same side and in the lumbar region to the opposite side.

The principal muscles flexing the spine are the psoas, rectus
abdominis, and external and internal oblique. These muscles,
excepting the psoas, which has been previously described, are in
the front and side walls of the abdomen and, along with transver-
salis, which lies beneath them are commonly called the abdominal
muscles.

RECTUS ABDOMINIS

211

RECTUS ABDOMINIS.

A rather slender muscle extending vertically across the front of
the abdominal wall. The right and left recti are separated by a
tendinous strip about an inch wide called the linea alba (white line).

Origin. — The crest of the pubes.

Insertion.— The cartilages of the 5th, 6th, and 7th ribs.

Structure.— Parallel fibers, crossed by three tendinous bands.
The lower end of the rectus passes through a slit in the transversalis
and lies beneath it.

Fig.

124. — Rectus abdominis and internal
oblique. (Gerrish.)

Fig. 125. — External oblique.
(Gerrish.)

Action. — In standing position, with the pelvis as the fixed point,
the rectus will pull downward on the front of the chest, exerting
its force on two sets of joints: those of the ribs and those of the
spinal column. If the ribs are free to move, they will be depressed;
if they do not move or after they have moved as far as they can

212 MOVEMENTS OF THE SPINAL COLUMN

move it will flex the trunk. Unlike most muscles previously studied,
the rectus abdominis usually follows a curved line when at rest
and the first effect of its action will be to flatten the abdominal
wall so as to bring it into a straight line.

Isolated action of the rectus causes flattening of the front abdom-
inal wall followed by depression of the ribs and flexion of the spinal
column.

EXTERNAL OBLIQUE.

This muscle covers the front and side of the abdomen from the
rectus abdominis to the latissimus (Fig. 125).

Origin.— The front half of the crest of the ilium, the upper edge
of the fascia of the thigh, and the linea alba.

Insertion. — By saw-tooth attachments to the lower eight ribs, in
alternation with those of the serratus magnus and latissimus.

Structure. — A sheet of parallel fibers extending diagonally side-
ward and upward from the origin, the fibers of the pair forming a
letter V on the front of the abdomen.

Action.— -The line of pull is too nearly coincident with the line
of the rib it joins to give it much power to depress the chest. If
the muscle of one side acts alone it will pull the insertion forward
and downward, causing a combination of flexion, lateral flexion,
and rotation to the opposite side; if both muscles of the pair act
at once the lateral pull is neutralized, giving pure flexion of the
spinal column. The external oblique will tend to flatten the abdo-
men even more than the rectus because of its curved position around
the side and front of it.

INTERNAL OBLIQUE.

Situated beneath the externus, with fibers running across those
of the outer muscle (Fig. 124).

Origin. — The lumbar fascia, the anterior two-thirds of the crest
of the ilium, and the upper edge of the fascia of the thigh.

Insertion. — The cartilages of the 8th, 9th, and 10th ribs and the
linea alba.

Structure. — A sheet of slightly radiating fibers forming with the
opposite muscle a letter A on the front of the abdomen.

Action. — Pulling downward and sideward on the front of the
chest and abdomen, the internal oblique of one side will flatten
the abdomen, rotate to the same side, and flex the trunk; working
with its fellow it will cause pure flexion.

The rectus and the two oblique muscles of the abdomen act
together in all movements of vigorous flexion of the trunk, as in
rising to erect sitting position when lying on the back. Notice

SPLENIUS 213

that when the movement begins slowly, the head being lifted first,
the rectus acts alone, the obliques joining in when the shoulders
begin to rise. In lateral flexion the abdominal muscles of one side
act; in rotation, the external of the opposite side acts with the
internal oblique of the same side.

Paralysis of the abdominal muscles gives rise to an excessive
lumbar curve, produced by the unopposed action of the extensors.

The chief extensors of the spinal column are the splenius, the
erector spinas and its branches, and the oblique extensors, which are
usually named as several distinct muscles. It will also be remem-
bered that the latissimus acts indirectly to extend the spine. These
muscles of the back are best understood by studying them in regu-
lar layers, beginning at the surface.

First layer, trapezius and latissimus (Fig. 30).

Second layer, levator and rhomboid (Fig. 35).

Third layer, serratus posticus superior and inferior and splenius
(Fig. 126).

Fourth layer, erector spinse and its upper divisions (Fig. 127).

Fifth layer, the oblique extensors (Fig. 129).

SPLENIUS.

Situated on the back of the neck and upper part of the chest.

Origin. — The lower two-thirds of the ligamentum nuchas, and
the spinous processes of the seventh cervical and the upper five
thoracic vertebras.

Insertion. — The base of the skull and the transverse processes of
the upper cervical vertebras.

Structure. — For surgical purposes the splenius includes two dis-
tinct muscles, but the division is unnecessary here. Like all the
muscles acting on the vertebras at the back it has a series of origins
and insertions through its entire length, the fibers from a certain
origin being inserted four to eight vertebras above, so as to act on
all the joints of the spinal column within its range.

Action. — The pull of a single strand of the splenius is mainly
downward but slightly backward and toward the median line, so
that when one side acts alone it will rotate the upper vertebras.
When both muscles of the pair act together the rotary effects neu-
tralize each other, giving pure extension of the head and neck.
The splenius is especially important for maintaining erect position
of the head and neck. When it is weak or elongated the head and
neck droop forward, causing the worst feature of round shoulders.

214

MOVEMENTS OF THE SPINAL COLUMN

Fig. 120. — The splenitis and the serratus superior. (Gerrish.)

ERECTOR SPINiE.

A very large and thick mass of vertically directed fibers that lie
on each side of the median line through the whole extent of the
back (Fig. 127).

Origin. — The posterior one-fifth of the crest of the ilium, the
back of the sacrum, the spinous processes of the lumbar and the
last three thoracic vertebrae, and the transverse processes of all the
thoracic vertebrae.

Insertion. — The processes of the vertebrae, the angles of the ribs,
and the base of the skull.

Structure. — Beginning as a thick muscle arising directly from the
pelvis, the erector spinae has joining it as it passes upward fibers
arising from the processes of the vertebrae; as it reaches the level
of the last rib it divides into three parts. The inner part passes

ERECTOR SPINM

215

up close to the median line of the trunk, having a continuous series
of origins and insertions from the sacrum up to the level of the
scapulae, and is usually called the spinalis dorsi. The middle part,
which is the largest of the three divisions and called the longissimus
dorsi, passes upward along the line of the transverse processes as far
as the head, the higher divisions being called the transversalis cervicis
and the trachelomastoid; like the inner division, it has origins and
insertions all the way up. The outer division follows the line of
the angles of the ribs and is named from its attachments the ilio-
costalis; it is continued as the accessorius and the cervicalis ascen-
dens as far as the middle of the neck. The muscle is more strongly
developed in the lumbar and cervical regions than in the thoracic,
where it tends to become more and more tendinous as age advances.
The following diagram indicates the relations of the two erector
spina? and their parts.

Hip Left
Erector spinae

Sacrum

Iliocostalis
longissimus

Erector spinae
Hip Right

Longissimus
iliocostalis

Accessorius
transversalis
Spinalis dorsi
—Median line—
Spinalis dorsi
Trarsversalis
accessorius

Cervicalis

Ascendens
trachelomastoid

-Head

Cervicis

Trachelomastoid

cervicalis ascendens

Action. — The contraction of a single strand of the erector spina?
will draw the processes of two vertebra? closer together, and since
the axis or fulcrum for each vertebra is at the middle of its body,
the leverage is fairly good; the combined action of several strands
will evidently extend the spinal column. The structure of the
muscle, with its continuous series of origins and insertions, makes it
possible to extend one part of the trunk while permitting flexion
of other parts. The pull of one erector spina? without its fellow
will produce some lateral flexion along with the extension, and the
attachment of the iliocostalis and its extensions so far to the side
makes the lateral pull considerable. The external division of the
erector spina? will also have power to depress the ribs.

The latissimus is tendinous for some distance from its origin,
and its tendon is so thin a sheet that the erector spina? is readily
felt through it. By placing the fingers well back toward the median
line a little below the level of the waist one can feel the erector
spina? contract and relax in alternate bending forward and back-
ward, the muscle being hard when the trunk is being raised from a
stooping position, but as soon as the erect position is reached it
relaxes. The alternate action of its two halves can be felt while
walking; notice that it is the erector on the side of the lifted foot
that acts and that it relaxes when the weight is placed on that foot.

216

MOVEMENTS OF THE SPINAL COLUMN

THE OBLIQUE EXTENSORS.

This group includes the muscles known surgically as the com-
plexus, in the region of the neck, the semispinals, extending

■■■ ' //■,

Fig. 127. — The erector spinse.
(Gerrish.)

Fig. 128. — The oblique extensors.
(Gerrish.)

through the cervical and thoracic regions, the multifidus, the whole
length of the spine, and the rotators, in the chest region. They lie
beneath the erector spinse in the hollow seen on each side of the
median line (Fig. 129).

QUADRAT US LUMBORUM

217

Origin. — The transverse processes of the vertebrae.

Insertion. — The spinous processes of the vertebrae a little above
the origin.

Structure. — The fibers pass obliquely upward and inward from
the origin to a spinous process, usually four or five vertebrae above.

Action. — The pull is downward and to a less extent sidewise,
making the main action extension with some rotary effect when
the muscles of one side act alone. Like the erector, the fibers of
different levels can act separately, localizing the movement in a
certain region.

Fig. 129. — Inclining trunk forward, showing the erector spinse and the gluteus
maximus in action: E, erector spinse; G, gluteus.

QUADRATUS LUMBORUM.

The "four-sided muscle of the loins" is a flat sheet of fibers on
each side of the spinal column beneath the iliocostalis.

Origin. — The crest of the ilium, the iliosacral ligament, and the
transverse processes of the lower four lumbar vertebrae.

218 MOVEMENTS OF THE SPINAL COLUMN

Insertion. — The transverse processes of the upper two lumbar
vertebrae and the lower border of the last rib.

Structure. — A flat sheet of fibers directed mainly in a vertical
direction.

Action. — The downward pull tends to depress the twelfth rib,
and when one muscle acts alone, to flex the trunk laterally. It
will also tend to extend the spinal column, since the attachments
are behind the axes of movement of the several vertebral joints.
It is too deeply placed to admit of study on the living body.

FUNDAMENTAL MOVEMENTS.

Erect Position. — The ordinary erect position of the trunk in stand-
ing is maintained by a combined action of the flexors and extensors
of the spine and the extensors of the hip. The weight is poised on
the hip-joints, and as soon as the hips are slightly flexed the ham-
strings and the erector spinse can be felt in action to support the
weight, which would otherwise cause a fall; if the weight is thrown
back to a certain extent these muscles relax and the abdominal
muscles come into action. So slight a change of balance as that
produced by raising the arm forward is enough to bring the ham-
strings and erector spinse into action, and this can be felt plainly
if the arm is raised quickly; a quick depression of the raised arm
brings the abdominal group into action in turn. The iliofemoral
band prevents overextension of the hip and makes it unnecessary
for the flexors of the hip to act in such cases, but whenever the
movement throws much strain on it the flexors act to help it stand
the strain.

Bending Forward. — Bending forward as in reaching for an object
on the floor, is accomplished by a lengthening contraction of the
extensors of the hip and spine so as to allow the weight to flex those
joints and yet with enough contraction to prevent the flexion from
going too fast or too far; the ankles are extended during this move-
ment, in order to carry the hips back and prevent the weight of the
trunk from causing a fall. Rising to an erect position again requires
stronger use of the same muscles to extend the hips and trunk;
the flexors of the ankle pull the tibia to erect position.

Bending Backward. — Bending backward as in looking at an object
directly overhead, is accomplished by a lengthening of the abdom-
inal muscles, allowing the lumbar portion of the spinal column
to be overextended by the weight of the trunk. If the lumbar
vertebrae do not permit as much movement as is desired the knees
are flexed to add to the inclination; the flexors of the hip work
strongly in this position to supplement the iliofemoral ligament.
Standing with feet wide apart adds slightly to the tilt of the

FUNDAMENTAL MOVEMENTS 219

pelvis, as it slackens the ligament somewhat. The psoas muscle is
in a position to help the abdominal muscles sustain the weight in
the extreme inclination backward, but the abdominal muscles have
better leverage.

Bending Sideward. — Bending sideward is accomplished by relaxa-
tion of the flexors and extensors of the opposite side, allowing the
weight to bend the spine laterally. If the movement is slow these
muscles relax gradually; if it is to be made quickly, to the right,
for example, the flexors and extensors of the right side must act
to hasten it; if it is desired to bend farther than the weight will
carry the trunk against the resistance of the opposing muscles and
ligaments, the muscles of the right side must act to complete the
movement. The two groups on the left side must act to lift the
trunk to erect position again.

Twisting. — Twisting, so as to turn the face to the right, will take
place mainly in the hip-joints unless movement there is prevented;
if it takes place it will be mainly inward rotation of the right hip
by the gluteus medius and outward rotation of the left by the group
of outward rotators. Rotation of the spinal column, which may
take place far enough to turn the shoulders about 45 degrees in
most cases, is caused (to the right) by the right splenius and internal
oblique acting with the left external oblique and the left oblique
extensors. Some authors include the serratus magnus and rhom-
boid among the rotators of the trunk, looking upon the right inter-
nal oblique, left external oblique, and the left serratus and rhom-
boid as a continuous spiral band of muscle connecting the right
hip with the left side of the spinous processes in the upper chest
region.

Sitting Erect. — In sitting erect without resting against a support
the trunk is poised upon the tuberosity of the ischium of each side
by the action of the hamstring muscles and the flexors of the hip.
The flexors and extensors of the trunk act as in standing. The hip
being flexed through 90 degrees, the iliofemoral band is not of
service and the flexors must act. The hamstrings are elongated a
little more than in standing position, the flexion of the hip not
being quite compensated by the flexion of the knee. The trunk
can be bent forward from sitting position until the chest touches
the thighs; the action of joints and muscles is the same as in stand-
ing except that the hamstring muscles stop the movement sooner.

Creeping. — Creeping, a form of progression on the hands and
knees used by nearly all children before they learn to stand, is
essentially the same as regards position of the trunk as the natural
position of quadrupeds. Here the trunk is supported at its two
extremities and its weight tends to make it sag in the middle,
which would be an extension or an overextension of the spine.

220 MOVEMENTS OF THE SPINAL COLUMN

The abdominal muscles, as the flexors of the spine, have to prevent
this movement and hold the trunk partly flexed. As a result the
young child, like the quadrupeds, is apt to have strong abdominal
muscles, while they are often weak in the adult through disuse.

GYMNASTIC MOVEMENTS.

Since exercise for the flexors of the trunk is so generally lacking
in common occupations, and especially so in school and college life,
graded work for this group of muscles is especially important in
gymnastics. The impossibility of over-extending the hip joints
makes it necessary to choose other than standing positions for these
exercises. Sitting, leaning, lying and hanging positions can be used
to advantage.

Fig. 130. — The leaning position, used for the abdominal exercise it gives.

Leaning Forward. — Leaning forward with the weight supported
by the hands placed upon something at the height of the chest is a
mild exercise of the quadruped type, and one that can be gradu-
ally varied toward the quadruped position by lowering the object
of support. The schoolroom affords opportunity for four stages
of the progression : hands on the wall, hands on the desks, hands on

GYMNASTIC MOVEMENTS 221

the seats, and hands on the floor. Flexing and extending the arms
in leaning position, with the hands at either of the heights, adds to
the severity of the work and affords variation to sustain the inter-
est of the pupil. (See Fig. 161) . It is usual to keep the hips extended
in leaning positions, as shown in Fig. 130.

Inclining Backward. — Inclining backward from sitting position
(Fig. 131) is a convenient way to exercise the abdominal muscles and
the flexors of the hip, but it requires a bench and some means of
holding the feet down to prevent falling backward. This movement
is used extensively in Swedish gymnastics with the feet placed under
the lower round of the wall ladder, which is constantly present on the
walls of Swedish gymnasia and schoolrooms. It differs from the
backward bend while standing, in that the iliofemoral band is lax
and will permit the hip to extend through 90 degrees. This exer-
cise, like leaning forward, permits one to grade the severity of the
strain on the abdominal muscles, since the force required to sus-
tain the weight increases slowly at first and later more rapidly,
the weight acting on the lever with full force only when the hori-
zontal position has been reached. Raising the arms forward lessens
the strain somewhat in the first stages of the movement by moving
the center of gravity forward; holding the arms in higher positions
increases it by moving the center of gravity up away from the
axis. The average person unused to gymnastic work can usually
incline backward through 30 degrees safely; the horizontal posi-
tion, especially if the arms are held high, is severe enough for the
most vigorous athlete. To avoid cultivation of bad postures, the
erect sitting position should first be taken and then the inclination
made in the hip-joints only.

Lifting the Knees. — Lifting the knees while hanging by the hands
is another excellent movement for development of the flexors of the
hip and spine, but it requires apparatus to support the weight and
is unsuited to subjects with very weak arms. The strain on the
abdominal muscles can be graded as finely as desired, since it is
possible to raise one or both limbs, raise them through any angle
up to 150 degrees, and the weight arm of the lever can be varied
considerably by flexion or extension of the knees. The function of
the abdominal muscles here is to hold up the front edge of the pelvic
basin, which would otherwise be depressed by the pull of the flexors
of the hip, and in case of lifting the knees above the level of the hip
to raise the front edge of the pelvis through flexion of the spinal
column.

Lifting one knee while standing on the opposite foot is often
used as an abdominal exercise, but it brings the abdominal muscles
into action too mildly to be of much use, the pelvis being held in
normal position by the hamstring muscles of the supporting limb.

222

MOVEMENTS OF THE SPINAL COLUMN

If the limb is raised to horizontal with knee straight there is a mild
action of the abdominal group, to about the same degree as in
walking. Teachers of gymnastics and athletic trainers have greatly
overestimated the effect of this exercise to develop the abdominal
muscles, overlooking the action of the hamstring group to hold
up the pelvis when standing on one foot. By throwing the knee up
violently, especially when the supporting knee is allowed to bend
and the pelvis is flexed, the abdominal muscles come into action,
but the posture is bad.

Fig. 131.

-Inclining backward from erect sitting position: R, rectus abdominis;
E, external oblique ; F, flexors of hip.

Lifting the Feet. — Lifting the feet while lying on the back is
accomplished by the same muscles as the preceding exercises but
is less suitable for beginners and weak subjects because the move-
ment begins at the point where the work is greatest. The weight
of the limb, pulling at right angles to the weight arm when the
muscles are at rest, requires the most force to lift it through the
first few inches, the strain gradually diminishing as the limb is
raised toward the vertical, where it becomes nothing. The amount
of work can be graded by varying the length of the weight arm

GYMNASTIC MOVEMENTS . . 223

by flexion of the knee. When the knees are allowed to separate
widely as they flex the feet can be drawn up toward the hips with-
out using the abdominal muscles; then by lifting the flexed limbs
the latter are used moderately. When the knees are kept close
together as they are flexed the abdominal muscles act in both the
knee flexion and the elevation of the limbs. When the flexed
limbs have been lifted the movement may be made a little stronger
by extending the knees and then lowering the limbs slowly to the
floor.

Lifting one Limb. — Lifting one limb while lying on the back is
often used as an exercise for the abdominal muscles with the thought
that it is just like lifting both limbs but milder, leading up to and
preparing for the stronger exercise. It is evident that raising one
limb is as vigorous work for the flexors of the hip as lifting both,
since the muscles of each side have to lift the limb of that side in
either case. One would suppose on first thought that lifting one
limb will bring the abdominal muscles into mild action as in hang-
ing position, having to support one limb instead of two, but feel-
ing of the front wall of the abdomen while one foot is slowly lifted
from the floor shows that these muscles do not act at all in this
case. The explanation is that the duty of the abdominal muscles,
to hold the front edge of the pelvis up against the pull of the hip
flexors, can while one limb is lifted be more easily done by the ham-
string muscles of the other limb, which are very much stronger
than the abdominal group and are here in a position to act, since
the floor prevents the femur from moving backward. When, how-
ever, the feet are separated widely on the floor the raising of either
limb requires a mild use of the abdominal muscles, the hamstring
muscles of the opposite limb contracting but not in a position to
hold the pelvis firmly in place.

Rising to Erect Sitting Posture. — Rising to erect sitting posture
from horizontal position on the back brings the flexors of the hip
and spine into strong action, but the movement is not suitable for
any but the strongest subjects because, like raising the feet from
the same position, it begins at the point of greatest strain and
because, unlike lifting the feet, it cannot be graded in severity by
a preliminary movement. It is made slightly less vigorous by
raising the head first as high as possible, but to do this the rectus
contracts strongly while the obliques are relaxed, pressing the
abdominal organs against the lax side wall of the abdomen with
danger of causing hernia in weak subjects.

Exercises on Chest Pulleys. — Exercises on chest pulleys with the
back toward the machine give work for the abdominal muscles
varied in force by the weights used and by the kind of movement
employed. Starting with arms at front horizontal the elbows may

224

MOVEMENTS OF THE SPINAL COLUMN

Fig. 132. — The Roberts "chopping" exercise for development of the extensors of
the hip and spinal column. Starting position.

Fig. 133.-

-The Roberts "chopping" exercise for development of the extensors of
the hip and spinal column. The finish.

GYMNASTIC MOVEMENTS 225

be flexed and extended, bringing hands to shoulders and thrusting
them forward in rhythm; the arms may be swung downward, side-
ward, or upward and back to front horizontal; combinations of
different ones of these with right and left arms may be used. To
make the balance problem easier it is best to stand with one foot
advanced.

Exercises on the chest pulleys with face to the machine, often
used for development of the trapezius, rhomboid, teres major and
latissimus, at the same time give strong work for the extensors of
the hip and spine, to hold the trunk firmly erect as a basis for the
action of the arm muscles. The same is true of the familiar " chop-
ping" movements of the Roberts dumb-bell drill, in which the
bells, first raised over one or the other shoulder, are swung far
down beside or between the knees, which completely stretches the
extensors, and then the body is raised to full height again, which
brings them into strong contraction. Another familiar gymnastic
movement with similar effect is the "leaning hang," with the body
inclined backward, perfectly straight from head to heel, and kept
from falling by the arms through grasping bars or rings. (See
Fig. 175.)

QUESTIONS AND EXERCISES.

1. Pick out from a set of unmounted vertebrae a cervical, a thoracic and a lum-
bar vertebra. Point out their special differences and show from their shapes why
rotation of the spine diminishes as we pass downward.

2. Study the action of the trunk in rowing, and state which muscles work in each
movement.

3. Study upon yourself the action of the gluteus medius and the erector spinse in
walking, by placing the hands so as to feel their contraction. Does the gluteus medius
act with the erector of the same or the opposite side?

4. What muscles of the trunk are most used by waiters ir> carrying a heavy tray
of dishes in front of the chest? Why do they lean back? Explain advantage and
disadvantage of holding it overhead.

5. Two men pull a heavy roller, both walking forward, one pulling on a handle
in front of the roller with arms behind him and the other pushing against the rear
of the frame. What muscles will each man rest when they change work?

6. Study the action of the trunk muscles in exercises on pulley machines, (a)
with face to the machine, (b) with back to the machine, (c) with side to the machine.
Tell what muscles of the trunk act in each position and also what muscles of the
hip-joint act in these same movements.

7. What trunk muscles are usually brought into action in pushing and striking?
In lifting? Is boxing better exercise for a baggage man or for one whose work is
mowing and rolling a lawn?

8. Watch twenty different persons walk, standing behind them, and make a note
of how many drop the free hip at every step, how many lift it, and how many bend
the trunk sidewise. Report.

9. A light stick three feet or more in length held against the back of the hips by
the hands while walking makes it easy to detect any rotation of the hips, since the
stick magnifies the extent of the swing. Try this on yourself and on several others,
and find how many do not swing the hips. Try the effect of length of stride. Strap
such a stick to the hips and another to the shoulders and see them move when the
arms swing freely during the walk.

10. Study the association of arm and leg movements in the common breast stroke
in swimming, and tell just how it is done. What are the main groups of muscles
used in propelling the body through the water?
15

CHAPTER XII.
BREATHING.

Breathing is a rhythmic expansion and contraction of the
chest, causing air to flow into and out of the lungs. How and why
these movements of the chest cause the flow of air is the first
question that presents itself.

The chest is an air-tight box having the ribs as its sides and the
diaphragm as its base, and containing within it the heart and
lungs. The lungs are elastic air sacs able to contain, in the average
adult, about 350 cubic inches of air. The elasticity of the lungs,
due to elastic tissue and to involuntary muscle fibers in the walls
of the bronchial tubes is sufficient to expel most of the air they
contain. This is well illustrated by inflating a pair of lungs removed
from the body of an animal and then releasing the pressure; they
quickly collapse as the air escapes through the trachea. Under
normal conditions the lungs fill all the chest room not occupied by
the other organs; they do not collapse like the isolated lungs,
although they are freely open to the outer air through the trachea.
The explanation of this is that the isolated lungs receive the pressure
of the atmosphere both on their inner and outer surfaces, so that
it has no effect, and the elasticity of the lungs acts unopposed,
while in the normal lung the atmospheric pressure on the outer
surface is prevented by the resistance of the chest wall, with the
result that the atmospheric pressure within the lungs inflates them.
The correctness of this explanation is shown by the fact that the
lungs collapse if the chest wall is punctured.

As long as the chest is without movement the air-pressure within
the lungs is the same as that outside, but as soon as the chest cav-
ity is enlarged the pressure within is diminished and the constant
pressure of the outer air forces more in through the trachea until
the pressures balance agairi. When the chest becomes smaller the
opposite flow of air occurs. The flow of air to and from the lungs
is seen therefore to be controlled by one constant force — the atmos-
pheric pressure — and two varying forces — the elasticity of the lungs,
which varies with the extent of inflation, and the size of the chest
cavity, which varies with muscular action.

The next question that presents itself here is how the size of the
chest cavity is altered in breathing. The change takes place by
two separate movements — the lateral expansion of the chest wall

BREATHING

227

and the depression of its base. To explain the first we must observe
the manner of movement of the chest wall.

The framework of the chest consists of the thoracic vertebrae,
the twelve pairs of ribs, the costal cartilages, and the sternum.
The costal cartilages join the ribs to the sternum; at the ends of
the ribs are arthrodial joints, permitting a slight movement at the
junction with the cartilages and somewhat more at the junction
with the spinal column. The movement is mainly an elevation and
depression of the ribs on their spinal joints as axes, with some

Fig. 134. — Position of the lungs in the chest. (Gerrish.)

rotation of each rib on the axis passing through its two extremities.
In the resting position the ribs slant downward at an angle of 15 to
20 degrees from the horizontal, and, as a consequence, their eleva-
tion carries the sternum and the whole front of the chest away
from the spinal column, as shown in Fig. 135. This enlarges the
chest from front to rear; since the ribs slant downward and side-
ward where they joint the spinal column, this elevation will increase
the lateral diameter of the chest as well. In order to expand the
chest, therefore, there must be muscular action that will lift the ribs.

228

BREATHING

The muscles acting to raise the ribs in quiet normal breathing
are the external intercostals, the diaphragm, and probably the
internal intercostals.

Fig. 135. — Enlargement of the chest by elevation of the ribs. (Gerrish.)

EXTERNAL INTERCOSTALS.

Eleven sheets of muscular fibers located in the spaces between
the ribs (Fig. 136).

Origin. — The lower borders of the first eleven ribs.

Insertion. — The upper borders of the last eleven ribs.

Structure. — Short parallel fibers extending diagonally forward
and downward, in the direction of the external oblique. It extends
from the spinal column forward to the costal cartilages, being
absent next to the sternum.

Action.— The pull is evidently calculated to draw the ribs closer
together. Duchenne reports that stimulation of the external inter-
costal muscles causes a lift of the rib below, without depressing
the rib above. Although the action has been in dispute it is now
generally agreed that the external intercostals act to lift the ribs
in inspiration.

INTERNAL INTERCOSTALS.

Eleven muscular sheets just beneath the external intercostals.

Structure. — Fibers extending downward and backward, like the
internal oblique. The muscle extends from the sternum backward
as far as the angles of the ribs, being absent next to the spinal

INTERNAL INTERCOSTALS

229

column. The layer of muscular fibers is about half as thick
the external.

The origin, insertion and action of the internal intercostals is
still an unsettled question.

Few topics of anatomy have been so long and bitterly disputed
as the action of the intercostal muscles. Disagreement is not sur-
prising, for the question is important and difficult. These muscles
are too deeply covered by other muscles to permit of study on
the normal living subject and the mechanical problems are compli-
cated and confusing. The first one to make a practical study of

INTERNAL INTERCOSTAL SEEN^
THROUGH ARTIFICIAL GAP IN
EXTERNAL

■ \ \ f* c °s - ■«

XT'/

\ M
Fig. 136. — The intercostal muscles. (Gerrish.)

the matter was Galen, physician to the Roman emperor in the
second century. He discovered by experiments made on living
animals that the intercostals and the diaphragm are breathing
muscles, and he taught that the upper intercostals, external and
internal, lift the ribs and that the lower ones depress them. His
view was accepted by all scholars for more than twelve centuries.
In the sixteenth century Vesalius, a Belgian, trained in the univer-
sities of Louvain and Paris, and chosen professor of anatomy at
the three leading universities of Italy in succession, taught that
the intercostals are both depressors of the ribs and muscles of
expiration. Aranzi, who followed him shortly in the university of
Bologna, taught that the intercostals have nothing to do with

230

BREATHING

breathing, except as passive portions of the chest wall, and von
Helmont, a famous scholar of Amsterdam, held the same opinion.
Magendie and Cruveilhier, well-known French anatomists, said
that the intercostals are at the same time elevators and depressors
of the ribs, acting in both inspiration and expiration. The Bartho-
lins, father and son, professors of anatomy in Copenhagen during
the seventeenth century, taught that the two sets of intercostals
are antagonists, the internals being elevators of the ribs and the
externals depressors. None of these views are now held, but they
are interesting as showing how wide a range of conclusions have
been reached by leading scholars.

s s

*■ B c

Fig. 137. — Hamberger's model to show intercostal action. The bar mn represents
the spinal column ; op and qr, ribs ; pr, the sternum. In A the rubber band R slants
like the internal intercostals and in B like the external intercostals; in C both are
acting; s, pegs to hold rubber bands.

Two opposing theories of intercostal action still hold the field,
each having many supporters. One of these, attributed to Ham-
berger, of the university of Jena in the first half of the eighteenth
century, is the exact opposite of the view of the Bartholins, namely,
that the external intercostals lift the ribs and the internals depress
them. The main argument for this view is mathematical, and is
best explained by means of a model used by Hamberger, later
described by Huxley, and now frequently seen in class-rooms
where physiology is taught. It consists of four straight pieces of
wood so hinged together as to illustrate the positions of the spinal
column, the sternum, and two adjacent ribs, and the movements
of the latter (Fig. 137). Pegs are driven into the ribs so that one

INTERNAL INTERCOSTALS 231

can attach to them cords or rubber bands to represent either set
of intercostal fibers. When a rubber band is attached in the posi-
tion of the external intercostals it lifts the two ribs and the ster-
num; when it is placed in the position of the internal intercostal
fibers it depresses them. The action of this model is so convincing
that a large number of authors accept it as a complete demonstra-
tion of the Hamberger theory. This theory has found further sup-
port in results obtained by Martin and Hartwell, well-known
American writers. They found by observing the action in cats
and dogs that the external intercostals act in unison with the dia-
phragm, while the internal intercostals act in alternation with it,
from which they conclude, as Hamberger did, that the former are
muscles of inspiration and the latter of expiration.

The other theory claims that both sets of intercostal muscles
are elevators of the ribs, acting in unison in inspiration. It was
taught in the eighteenth century by Borelli, an Italian physiolo-
gist, Haller, a German physiologist, Cuvier, a famous French
naturalist, and Winslow, a French anatomist, all authorities in
their respective fields. Haller claimed to have seen the opposite
of what Martin and Hartwell report, namely, that the internal
intercostals contract in inspiration, and as early as 1747 he argued
that Hamberger's model does not prove anything because it does
not accurately represent the conditions of the chest; he attached
cords to the ribs of a real chest, fresh from the dissecting-room,
and showed that contraction of the internal intercostals will lift
the ribs, Winslow argued that since both sets of fibers between
two ribs tend to draw them together, and since the upper ribs are
less movable than the lower ones, both will help in lifting the ribs.
He also pointed out the presence of each set of fibers at the end of
the space where it must act to lift the rib below, and their absence
at the end of the space where they would do the opposite. If the
internals are expiratory, why are they omitted near the spinal
column, where they would pull directly from the vertebrae to
lower the ribs?

The second theory received still stronger support through the
work of Duchenne, who began in 1850 a long series of observations
and experiments upon living human subjects, patients in the hos-
pitals of Paris. He found cases who had lost all of the muscles
ever supposed to lift the ribs, excepting the intercostals, and in such
subjects he saw the chest rise and fall in normal rhythm in quiet
breathing; he saw and felt the external group, at the sides, and the
internal group, at the front, where the externals are absent, both
acting in unison with the movement of the chest wall. Again he
stimulated the intercostal muscles, in patients who had lost the
pectoralis major and serratus magnus, and found that isolated

232 BREATHING

action of either group lifts the rib below it, without depressing the
rib above. Then he stimulated the nerve which supplies fibers to
both groups and saw the same elevation of the rib — which should
not take place if the two sets are antagonists. He claimed that
isolated action of either set causes distortion of the chest, one set
pulling the ribs back and the other set pulling them forward;
therefore both sets must be used in unison in normal chest expan-
sion. Duchenne is an ardent supporter of Haller and Winslow
and attacks the Hamberger theory at every point.

Present-day text-books of anatomy are about equally divided
on the question of the action of the intercostals, Gray and Spalte-
holtz agreeing with Hamberger that the internal intercostals depress
the ribs, Morris, Cunningham and Piersol agreeing with Duchenne
that they act with the externals to lift the ribs, while Gerrish and
Sobotta say it is undecided, and Quain states both yiews. Every-
body seems agreed that the external intercostals lift the ribs, and
the fact that the internal set is of only half the thickness in the aver-
age subject makes the difference of less importance than it might
be. The arguments have been stated here in full because they are
good examples of scientific reasoning, and especially fitting in a
book like this, where the problems of muscular action are the main
subjects of study.

THE DIAPHRAGM.

A dome-shaped sheet, partly muscular and partly tendinous,
forming a partition between the thoracic and abdominal cavities.
The tendon is at the summit of the dome and the muscle fibers
along the sides (Fig. 138).

Origin. — An approximately circular line passing entirely around
the inner surface of the body wall. It is attached at the back to the
upper two lumbar vertebrae and the lumbar fascia; on the sides for
a variable distance, to the lower two ribs; at the front, to the six
lower costal cartilages and to the sternum.

Insertion. — The central tendon, which is an oblong sheet forming
the summit of the dome.

Structure. — The fibers pass vertically upward for some distance
from the origin, and then turn inward to their insertion. The fibers
of the sternal portion are shortest; the lateral portion has saw-
toothed attachments to the ribs and cartilages in alternation with
those of the transversalis, which is a muscle of expiration.

Action. — Contraction of the fibers of the diaphragm will evi-
dently pull down on the central tendon and up on the ribs and
sternum. Observation shows that it lifts the ribs slightly but
depressses its own central tendon as its principal movement. Obser-
vation also shows that it acts in unconscious breathing in unison

THE DIAPHRAGM

233

with the intercostals or nearly so. As it descends it flattens and
leaves more room in the chest, thus aiding the intercostals in enlarg-
ing the chest. Duchenne considers it the most important of the
breathing muscles, since he found it to be the only muscle that can-
maintain without much effort a sufficient flow of air to supply the
tissues when all other muscles of inspiration have been lost.

The relation of the diaphragm to the abdomen is important, as
well as its relation to the chest. When it descends it must of course
take from the abdomen just as much room as it gives to the chest.
It pushes the stomach, liver, and other abdominal organs before it,
and since these organs are soft and pliable but not compressible,
they crowd out against the abdominal wall. The soft and flexible

Fig. 138,

-The diaphragm.

(Gerrish.)

abdominal wall gives way, expanding on the front and somewhat
at the sides to make the needed room. If the abdominal wall is
thick and strong it offers considerable resistance to the descent of
the diaphragm, and this will increase the upward pull of the latter
on the ribs. The diaphragm always has to force out the abdominal
wall against the pressure of the atmosphere, which is considerable,
but the breathing is more efficient when the abdominal walls are
strong and well muscled.

Simultaneous contraction of the intercostals and diaphragm
expands the chest in all directions and thus produces inhalation;
in quiet breathing this is the only muscular action taking place
with the exception of the muscles in the walls of the bronchial

234

BREATHING

tubes, which are not of the same variety and not usually included
in studies of the muscular system. When the muscles of inspira-
tion relax, the air is expelled by the elasticity of the lungs, the weight
of the chest, and by the elasticity of the abdominal wall, the latter
forcing the diaphragm up to its resting position. In more vigor-
ous inhalation the intercostals and the diaphragm are assisted by
the sternocleidomastoid, scaleni, serratus posticus superior, pec-
toralis minor, and sometimes by the upper trapezius.

Fig. 139 - Fig. 140

Figs. 139 and 140. — Expansion of the abdomen by contraction of the diaphragm.
Fig. 139 shows the position of the abdominal wall in quiet expiration. Fig. 140
shows how it is protruded when the diaphragm contracts in taking a full breath.

STERNOCLEIDOMASTOID.

A pair of muscles forming a letter V down the front and sides of
the neck.

Origin. — The mastoid process of the skull.

SCALENI

235

Insertion. — The front of the sternum and the inner fourth of the
posterior border of the clavicle.

Structure. — Parallel fibers, dividing into two parts below its middle.

Action. — As a breathing muscle, it lifts the sternum, both muscles
of the pair acting together, while the head is held rigidly upright.
When the lower end is the fixed point, which is more usual, one of
the pair rotates the face to the opposite side and the two flex the
neck.

The sternocleidomastoid is an important muscle of respiration,
acting in labored breathing in such exercises as running or in making
a deep inhalation for any purpose. It is able to assist greatly in
cases where some of the other muscles of breathing are lost.

The lower portion of this muscle is shown well in Fig. 48.

Fig. 141. — The scaleni. (Gray.)

SCALENI.

Three muscles named the anterior, middle, and posterior scaleni
from their relative positions and their triangular form as a group
(Fig. 141).

236 BREATHING

Origin. — The transverse processes of the cervical vertebrae.

Insertion. — The anterior and middle scaleni, on the upper surface
of the first rib; the posterior on the second rib.

Structure. — Longitudinal fibers, tendinous at each end.

Action. — The scaleni are in a position to support the upper ribs
when the intercostals contract and to lift them by strong contrac-
tion, providing the neck is held firmly erect. The presence of the
brachial plexus of nerves makes it difficult to secure satisfactory
isolated action of the scaleni, but under the mild stimulus that can
be given them, the elevation of the first ribs and sternum has been
seen. The inability of the scaleni to sustain and lift the chest when
the neck is not held up is the most serious result of mild cases of
round shoulders.

SERRATUS POSTICUS SUPERIOR.

A flat rhomboidal sheet of muscular fibers lying beneath the
upper half of the scapula. It is shown in Fig. 126.

Origin. — The ligament of the neck and the spinous processes of
the seventh cervical and the first three thoracic vertebrse.

Insertion. — The second to the fifth ribs inclusive, beyond their
angles.

Structure. — Longitudinal arrangement with the ends tendinous.

Action. — The serratus posticus superior lies so deep beneath the
scapula and the trapezius and rhomboid that its action has not
been observed. Its position and attachments are such that all
agree that it is able to lift the ribs.

The act of breathing is one of the most interesting movements
to study on the living subject. In quiet breathing we can easily
see the expansion of the chest caused by the intercostals and the
expansion of the abdomen caused by action of the diaphragm,
although the muscles doing the work are hidden from view. With
a deep, full inspiration the sternocleidomastoid springs into view
and the scaleni can be felt behind it on the sides of the neck. The
pectoralis minor can usually be felt and sometimes seen, bulging
up beneath the major. The upper trapezius can be tested as
described in Chapter IV. These muscles show best when the
Subject takes the deepest possible breath or makes sudden inspira-
tory effort, as in sniffing.

Besides the regular breathing muscles just mentioned, the trape-
zius acts in deep breathing to sustain the scapula as a firm base
for the pectoralis minor, and the extensors of the head and neck
act to hold these parts firmly erect to support the action of the
sternocleidomastoid and scaleni. The cervicalis ascendens and

TBANSVERSALIS 237

the serratus posticus superior are in a position to lift on the ribs,
but their action cannot be seen or felt.

The list of inspiratory muscles usually given by authors of text-
books includes the muscles just studied and also the serratus mag-
nus, latissimus, and lower pectoralis major, but observation of
the living body does not justify it. All three of these muscles seem
to swell out in inspiration, but careful observation shows that it is
passive as far as they are concerned, the expansion of the chest
giving an appearance of contraction. No contraction of the ser-
ratus magnus can usually be seen or felt unless the arms are raised,
and then it acts as an elevator of the arm rather than as an elevator
of the ribs. Duchenne says that on stimulation of the serratus and
rhomboid at the same time the scapula is first raised considerably
and then the ribs are lifted, but nothing like this occurs in ordinary
breathing. By placing the hand on the tendons of the latissimus
and pectoralis major at the armpit any action of these muscles can
be felt; I have never been able to detect any action of the pectoralis
major in breathing, and only rarely any action of the latissimus.
An occasional subject brings into action in strong effort all the
muscles in the vicinity of the desired movement, whether they
can help in the performance of it or not, but that is not normal
coordination, and such subjects are not useful for studying normal
muscular action.

Normal quiet expiration seems to be performed without any
muscular action, but as soon as it becomes vigorous certain muscles
are contracted to expel the breath. This is also true in coughing
and sneezing,- which are sudden expirations to expel something
from the air tubes, in the production of the voice, as in talking,
singing, and shouting, and in laughing, crying and blowing wind
instruments. The muscles of expiration are the rectus abdominis,
external and internal oblique, transversalis, serratus posticus
inferior, latissimus, and perhaps the iliocostalis and the quadratus
lumborum. The internal intercostals also belong here if the Ham-
berger theory is correct.

TRANSVERSALIS.

This muscle forms the third layer of the abdominal wall next to
its inner surface.

Origin. — The lower six ribs, the lumbar fascia, anterior two-
thirds of the crest of the ilium, and the upper edge of the fascia of
the thigh.

Insertion. — It meets its fellow of the opposite side at the linea
alba.

238

BREATHING

Structure.— A thick sheet of parallel fibers crossing the abdomen
horizontally. Its middle part is thickest and also has the longest
fibers. Like the internal and external oblique, its muscular fibers
are placed chiefly at the sides of the abdomen. The front tendons

of the three fuse to form a single tendon
which is slit down the center to form a
sheath for the rectus abdominis.

Action. — The shortening of the trans-
versalis presses upon the abdominal
organs and acts through them to push
the diaphragm upward, the four abdom-
inal muscles working together in this
movement. Its upper part also pulls
the lower ribs forward toward the median
line.

SERRATUS POSTICUS INFERIOR.

Named from its position and its saw-
toothed insertion (Fig. 35).

Origin. — The spines of the last two
thoracic and first two lumbar vertebrae.
Insertion. — The last four or five ribs,
beyond their angles.

Structure. — The inner half is a tendin-
ous sheet blended with the tendons of
the latissimus and erector spinse. The
muscular fibers are inserted directly into
the ribs.

Action. — The fibers of the serratus
posticus inferior are in a position to
depress the ribs and the angle of pull
is large. As it will act in this case in
unison with the latissimus, at least in
some instances, its action is not easily observed on the living
subject.

In vigorous expiration, such as we have in coughing, sneezing,
singing, shouting, and blowing a wind instrument, the four abdom-
inal muscles can be felt in action and also the latissimus, which is
tested by feeling its tendon at the rear of the armpit. The ilio-
costalis and quadratus lumborum are not so surely felt to contract,
although they bulge out in the movement; the sudden pressure on
the abdomen produced by the action of the abdominal group makes
the wall suddenly tense everywhere, and it is not easy to tell whether
the muscles near the spinal column actually contract or not. Most

Fig. 142.— The transversalis.
(Gerrish.)

SERRATUS POSTICUS INFERIOR

239

subjects move the scapula in coughing, but there seems to be no
uniform manner of moving it, some lifting it, some adducting the
lower angle, and some adducting the whole scapula. The trapezius
acts in some cases and the rhomboid in others; it looks more like
a diffuse spread of impulses than a coordinated action. In expira-
tion with gradually increasing force the rectus abdominis can be felt
to act first, the others joining as the force increases.

In normal breathing the lungs are protected from injury that
might be produced through sudden and great changes in air-press-
ure by the manner in which the movements are performed. As
may be seen in the record shown in Fig. 143, the ribs are raised
slowly at first, gradually coming to the most rapid inhalation, and
then gradually slowing down, the inspiration ceasing when there
is only the slightest movement being made. Although expiration
in quiet breathing is said to be without muscular action, yet it is
controlled, as the record shows, in the same way, and this must be

jE7 E

III

At Rest
T\ ' ' 'I i~i i i i i i i i i i—i i i i i i

Subject, H
July li, 1903

r_n_

I I Working

i i i i i i i r~i i i i i i l I I

Fig. 143. — Graphic record of breathing movements: B, curve of breathing; T,
time. in seconds; I, inspiration completed; E, expiration completed.

done by gradual changes in the relaxation of the inspiratory muscles,
which act through the entire cycle of breathing, contracting in
inspiration and relaxing in the same manner in expiration. The
nerve center controls the two movements and the change from one
to the other much as a motorman stops and starts his car, so as to
avoid sudden jolts and still secure results promptly. We see the
difference when we notice how a sigh is produced, simply by sud-
denly and completely relaxing the muscles of inspiration when the
lungs are full; the characteristic sound is made by the sudden rush
of air out through the nose when the elastic forces that empty the
lungs are suddenly released, in marked contrast with the almost
noiseless manner of normal breathing. Yawning is similar in this
way to sighing, being a full inspiration followed by a sudden relax-
ation of the inspiratory muscles. Here the elastic cartilages and
ligaments of the chest, the ribs themselves, and the abdominal
wall are drawn tense as a bowstring by the full inspiration and
suddenly let go, discharging the air through the open mouth. The

240 BREATHING

same tendency to fail to control expiration is seen during fatigue
and in fever.

In all physical examinations the size and mobility of the chest
are items of the greatest importance. The size of the chest is im-
portant because upon it depends upon the amount of air the lungs
will contain, and the more air there is in the lungs the more of the
capillary area is exposed to the air and the greater is the gaseous
exchange. The size of the chest depends in part upon the length
of the bones that form its framework and in part upon the habitual
posture of the chest — the chest that is held high containing more
air than the one that is depressed. The size of the chest is usually
measured with the tape, although its depth and breadth are also
taken by some examiners by means of calipers. The girth of chest
of the average college man, as shown in Seaver's chart of Yale
students, is the same as the height sitting; in case of college women,
as shown by Miss Hill's chart of Wellesley students, it is only 86
per cent, of the height sitting; in Mrs. Clapp's measurements of
Nebraska women it is slightly above 86 per cent. Actual size of the
chest cavity, as measured with the tape, is subject to considerable
error due to different degrees of development of the muscles on the
outside of the thorax, and this is especially important in subjects
who contract during deep inspiration muscles not usually employed.

Mobility of the chest, quite as much as size, is a measure of the
efficiency of the lungs, indicating the extent to which the ribs can
be raised and the lungs filled. With a mobile chest the muscles
can more easily move the amount of air needed in quiet breathing
and the subject does not so soon reach his limit in exercise that
demands great increase of respiration. Many examiners still
measure mobility of chest with the tape, although the method is
liable to even greater errors than in determining its size. For ex-
ample, it is possible to still farther expand the chest after a complete
inspiration by closing the glottis and then contracting the abdom-
inal muscles; this forces the diaphragm upward and since the air
cannot escape through the trachea all the force of the abdominal
muscles is exerted upon the inner surface of the chest wall to force
it outward. The result is an increase in the measurement shown
by the tape, although no air is inhaled and the chest is not really
enlarged; the subject has by a trick enlarged the chest at the exact
place where the examiner is measuring it; many a man with a poor
chest has passed his examination for life insurance by deceiving
the examiner in this way. The best test of lung efficiency is that
made by means of the spirometer. The subject fills his lungs as
completely as possible and then exhales as completely as possible
into the mouth-piece of the spirometer and the amount of expired
air is read directly on the scale. Since the movement of the chest

SERRATUS POSTICUS INFERIOR

241

is of value only as it causes movement of air, the spirometer test
is the best that can be made; it also shows the effect produced by
depression of the diaphragm as well as by elevation of the ribs.

The spirometer test is really a test of strength, since the best
record can be made only by the greatest possible action of the
inspiratory muscles followed by the greatest possible action of the
expiratory muscles. Practice in using the spirometer will increase
ability to breathe effectively by increasing the strength of the
muscles and increasing the mobility of the chest. Hutchinson,

Fig. 144. — The spirometer: A, air tank; B, retainer partly filled with water; C,
breathing tube; d, mouth-piece; a, b, c, stop-cocks; g, counterweight. (Reichert.)

who first used the spirometer for scientific purposes, pointed out
that the average individual in quiet breathing moves in and out
from 25 to 30 cubic inches of air (tidal air); he can inhale about
100 cubic inches more than is taken in quiet inspiration (comple-
mental air) and can exhale about 100 cubic inches more than is
exhaled in quiet expiration (reserve air); after the most complete
expiration about 100 cubic inches of air (residual air) still remains
in the lungs. Some objection has been raised to the use of the
spirometer because of the inability of subjects to make the same
record repeatedly at first; this is always a difficulty with strength
16

242 BREATHING

tests, and disappears after a few careful trials, if the subject takes
pains to make complete inspirations and expirations, without has-
tening during the expiration; air is often lost around the mouth-
piece and through the nostrils if too much force is used. The
breathing capacity of the average college man, according to Seaver,
is 253 cubic inches; that of the average college woman, according
to Miss Hall, is 150.3 cubic inches. These figures are about 5 per
cent, too low because the spirometer is usually at a temperature
20° below that of the body and the air blown into it is cooled and
thereby shrinks before the reading is made.

The chest is relatively deep and narrow in infancy and becomes
broader and flatter as age advances. This change is more rapid in
some cases than in others, so that in the examination of high school
and college students both types are seen — the broad, flat chest
and the deeper and narrower type. McKenzie has found that in
college men the deep-chested type has greater breathing capacity
than the broad and flat type; he also finds that the chests of ancient
Greek athletes, as shown by classic statuary, are of the deeper and
narrower type. On the other hand, Woods Hutchinson and others
claim that the broad and flat chest is the normal adult type and
that the narrow and deep chest is a case of arrested development
and a menace to health.

The nervous mechanism that controls the breathing muscles
works automatically, regulating the amount of movement to suit
the needs of the body while sleeping and waking, rest and exercise,
without any attention being directed to it. Nevertheless, these
movements are subject to the will and may at any time be modified,
as to rate, depth, and even as to form by the will. This makes the
breathing movements subject to educational influence and enables
one to change his habitual coordination, just as he can in throwing,
walking, or talking, by persistent practice of a different style. In
this way singers often change their habitual method of breathing,
first by a conscious effort and later unconsciously, developing a
form of inhalation and exhalation that some teacher considers best
suited to the production of the voice. For example, singers are
taught to hold the chest high habitually and to habitually take
the next inspiration before, the chest is fully depressed, since the
expanded chest acts as a sounding box for the voice and gives a
better tone. Some of these teachers of voice culture train their
pupils to keep the abdominal muscles contracted in inspiration so
as to prevent the use of the diaphragm and emphasize costal breath-
ing; others teach them to hold the chest expanded and use the dia-
phragm as much as possible in taking the breath. The extent to
which it is possible to gain control of the individual muscles of
breathing so as to inhale and exhale in a variety of ways, is sur-

SERRATUS POSTICUS INFERIOR 243

prising. Athletes also learn to breathe in ways that will accord
with the movement that is being made, as it economizes nervous
and muscular force to do so.

One consequence of our ability to change the coordination of our
breathing muscles by practice is the variety of habitual methods
of breathing we find when we observe many individuals, as we
have occasion to do in physical examinations. In quiet breathing
many subjects use the chest movement exclusively while others
use only the diaphragm, and in taking deeper breaths they begin
in the same way, bringing in the other movements in later stages.
This gives what are called the costal and the abdominal types of
breathing. Investigations have shown that men tend to use the
diaphragm chiefly and women the chest, and it was formerly
believed that something in the structure of the female led to her
using costal breathing. More study of the questions shows that
it is mainly a change of habitual coordination produced by habits
of dress, the constricted waist producing costal breathing by pre-
venting movement of the abdominal wall. The two types are not
universally found in the two sexes, however, some women who
have not worn corsets breathing like men and some men who have
worn belts breathing like women. Children generally breathe by
a combined costal and abdominal movement, as do many adults.
For purposes of health it is usually considered of no consequence
how one takes the breath so long as he gets air enough; still there
are some who favor particular types of breathing on the ground
that certain parts of the lung are especially liable to disease and for
that reason those parts need to be aerated frequently.

In taking the deepest possible breath, as in making a test with
a spirometer, the costal and abdominal types of breathing are
noticeable. Some subjects expand the chest and the abdomen
through the entire movement, while others begin to constrict the
abdomen as soon as they reach the point where considerable effort
is Used. This has always seemed to me to be a faulty coordination,
the contraction of the abdominal muscles preventing the taking of
a full breath. Some writers believe that a certain amount of con-
traction of the abdominal muscles is needed to enable the diaphragm
to lift the lower ribs, making this form of breathing as efficient as
the former. Campbell says that the lungs are filled before the chest
is completely lifted, and that the stronger chest muscles overcome
the diaphragm and suck it upward and the abdominal wall inward;
this view does not seem to me justified, since if the lungs were so
small we would not so easily get the rapid increase of breathing
capacity that readily follows practice in deep breathing.

Two kinds of exercises for the development of the lungs are
recognized in physical education: voluntary deep breathing and

244 BREATHING

the securing of increased respiration by running and similar exer-
cises that call for greater elimination of carbon dioxide. Each
method has its advocates and its advantages.

Voluntary deep breathing can be taken by those who cannot
endure vigorous exercise and under conditions that make the latter
impossible; this makes it a practical method to use at all ages and
as a regular routine when varying conditions break up habits of
general exercise. The practice aerates the rarely used portions of
the lungs, gives work to the muscles, and increases the mobility
of the chest. The Swedish system wisely directs that voluntary
breathing exercises be given at the end of the exercise period, when
the need of air has been increased by the exercise. The. Swedes
here arranged an elaborate series of arm movements to accompany
the breathing exercises and make them more efficient, but recent
studies have shown that all such movements hinder rather than
help the most complete filling of the lungs, so that they are useful
only to give variety and make pupils think they are doing something
different.

QUESTIONS AND EXERCISES.

1. What is the advantage gained by raising the head and shoulders to full height
when one wishes to take a full breath? Test with a spirometer whether you can
actually take in more air when you do this, and if so, how much more.

2. Explain how increased mobility of the ribs can make one able to run better.
Will it be more useful in sprinting or long distance running?

3. Explain how tight clothing may result in strengthening the breathing muscles.
Will it have most effect on inspiratory or expiratory muscles? What objection to
this method of developing these muscles?

4. Explain how the lower serratus can help in taking a full breath; the splenius;
the upper trapezius; the middle trapezius.

5. Study upon yourself the action of the abdominal muscles and find what part
of the muscular wall is contracted in the ordinary use of the voice in speaking; in
loud talking; in whistling; in singing; in blowing, as in inflating a ball. Is the mus-
cular contraction distributed evenly over the abdominal wall or is it localized? Is
it the same or different in the different exercises?

6. Test the effect of compressing the waist with a strap on your ability to take a
full breath, as shown by the spirometer. How many inches can it be compressed
before an effect is produced on the record you can make? Has this any relation to
the advisability of wearing belts or tight clothing about the waist?

7. What measurements must be made with the tape line to test a person's breath-
ing ability as a spirometer tests it? Why cannot the test with the tape be as good
as the spirometer test?

8. A pneumatometer is an instrument to test the force of exhalation. Why is
this test less valuable in a physical examination than the spirometer test? Why is
it more liable to injure the lungs?

9. How can you explain the fact that long distance runners are often unable to
make a high record on the spirometer? Would it help them to practice deep breath-
ing exercises? What good would it do them?

10. The Kellogg dynamometer (Fig. 7) tests the strength of separate muscle
groups. By placing a strap around the waist and attaching it to the dynamometer
one can exert a force of 150 pounds, the abdominal wall pressing out on the strap
to give the force. What muscles are used here? Is there any chance of injury in
using this test? How and upon what tissues?

CHAPTER XIII.
THE UPRIGHT POSITION.

Man's erect posture is an advantage to him in many ways, the
most important of these being the freeing of the hand, its develop-
ment for more skilful and useful movements and the resulting
greater development of the brain. The erect posture has also some
disadvantages, and most of these, when carefully observed, seem
to be due to change to upright position of structures primarily
intended for use in the horizontal position.

One illustration of this lack of adaptation to the erect posture is
seen in the placing of valves in the veins. A vein in which blood
flows upward needs valves, but one in which it flows horizontally
does not. Now the intercostal veins convey blood upward in quad-
rupeds while the vena cava and the portal veins convey it horizon-
tally, and to meet this condition there are valves in the former but
not in the latter. In the human body, shifted to the erect posi-
tion, the vena cava and the portal system need valves and the inter-
costal veins do not — yet we are supplied with valves just as they
are in the quadruped, much to the disadvantage of the circulation.

The location of the vermiform appendix is a similar instance. The
upright position shifts this structure from the highest level of the
digestive tract in the quadruped to the lowest level in man, where
it is subject to much greater pressure and liable to irritation by
fragments of food forced into it by changes in pressure.

In quadrupeds the ribs and sternum hang below the spine and
swing back and forth in breathing like a pendulum, requiring very
little muscular expenditure, but when this mechanism is shifted
to upright position the full weight of the chest wall must be lifted
with each breath and held up to proper level all the time by
muscular action.

Two of the most important muscles for movement of the limbs —
the serratus magnus and the gluteus maximus — take part in
coordinated movement, as we have seen, only when the limbs are
in the position in which quadrupeds use them — nearly at right
angles with the body.

When we come to study posture we find other instances of lack
of adaptation of the body to erect position. The spinal column
seems to have been primarily intended for swimming and crawling

246

THE UPRIGHT POSITION

animals, later adapted to use by quadrupeds, only at a compara-
tively recent time put to use in the erect position and not yet
suited fully to that position. It is helpful, therefore, to notice some
of the conditions present in the skeleton" of the lower vertebrates
preliminary to a study of the erect posture.

The general form of the trunk, common to all vertebrates, is
roughly cylindrical with a cross-section like that shown in Fig. 145.
The muscular body wall contains the vital organs and the spinal
column is placed in one side of it. This is the fundamental struc-
ture that must be adapted to the erect position. Let us first notice
how it is adapted to the condition of the quadruped.

EXTERNAL OBLIQUE
INTERNAL OBLIQUE
TRANSVERSALIS

LATISS1MUS

ERECTOR SPIN^E

Fig. 145. — A cross-section of the trunk. (Gerrish.)

In quadrupeds the horizontal trunk is supported at two points:
by the forelimbs at the shoulder girdle and by the hindlimbs at
the pelvis. When a segmented column like the spine is supported
at two points, as it is here, the best form for it is the arch, as is
well known in architecture. The quadruped spinal column, as
shown in Fig. 146, is a flat arch which may be called the "primitive
arch" to distinguish it from the human spine with its three curves.
The weight of the trunk pulls down and tends to flatten the arch,
while the abdominal muscles easily hold it up. The internal organs
hang by their ligaments at right angles to the spine and are sup-
ported without any tendency to displacement by the muscular
body wall. The bodies of the vertebrae are thinner on their lower

THE UPRIGHT POSITION 247

edges, their shape aiding also to maintain the arch of the spine. The
quadruped position is a stable and economical one, with no apparent
difficulties in the maintenance of normal posture.

The crouching start used by the sprinter imitates fairly well the
normal position of quadrupeds (compare Fig. 188). Notice that
the knees are flexed to about a right angle, the thighs slanting for-
ward about 45 degrees. To shift from this position to the erect
one he must raise the trunk through 90 degrees and extend the
knees, making a total angular movement of 135 degrees. Notice
also that as one rises from the horizontal to the upright position
he begins by extending his hip-joints and finishes by extending his
lumbar spine. The orang-outang and other apes make the entire
movement in the hips and retain the primitive arch of the spine
as they stand up. Which way is best?

Fig. 146. — Skeleton of the horse. (Chauveau.)

This raises the fundamental question, What is the ideal standing
position? The ideal posture must satisfy at least two require-
ments: it must be economic of muscular expenditure and it must
put the vital organs in a favorable position for performing their
functions.

A jointed framework like the vertebrate skeleton can support a
weight in upright position with least muscular expenditure when
its segments are in a straight line. With regard to the body as a
whole, therefore, Miss Bancroft's "window pole test" sets the best
standard, classing all postures as faulty that put the body segments
in a zigzag instead of a straight line.

To rise to erect position, as the orang-outang does, by an angular
movement of 135 degrees in the hip-joints, makes a marked zigzag

248 THE UPRIGHT POSITION

in the framework, for it carries the iliosacral joints directly behind
the hip-joints. By a comparison of the two skeletons it is easy to
see how this fault is avoided in the human body. The pelvic basin
in man, instead of being tilted to the flat position it takes when the
orang-outang stands up, is stopped in an oblique position by the
iliofemoral ligaments and the erect position of the trunk is secured
mainly by a sharp bend of the spinal column where the sacrum
joins the lumbar spine. This angle, known as the sacral angle, is
almost 45 degrees in normal subjects. There is also a slight rever-
sal of the primitive arch in the lumbar region (Fig. 122).

The normal sacral angle brings the pelvis and spine in such posi-
tions that the top of the sacrum is slightly behind the line between
the hip-joints, so that the weight of the trunk when held erect
tends to extend the hips with a very slight force. The development
of the sacral angle in man is plainly an advantage over the primi-
tive arch which the apes retain when they stand erect, as far as
economy of force is concerned.

There is another reason why the human spine, with its sacral
angle and reversal of the primitive arch in the lumbar region, is an
improvement over the form found in the apes. The shift to upright
position causes the internal organs to hang downward lengthwise
of the body cavity instead of across it. The result is that the stom-
ach, liver and intestines tend to sag down and bear their weight
on the organs lying below them while the whole mass of viscera
tends in the same way to rest upon the pelvis and press upon the
organs lying within it. This not only interferes with the function
and development of the pelvic organs but the weight of all the
viscera bears down the perineal muscles, that close the large open-
ing between the tuberosities of the ischii on the sides and the coccyx
at the rear. (See Fig. 147.)

The oblique position of the pelvis in the human body brings the
pelvic organs far to the rear, where they are beneath the sacrum
and protected by it from the weight of the organs above. These
organs, instead of resting upon the perineal muscles, are supported
by the arches and rami of the pubes. The sharp bend just above
the pelvis tends to separate the long cavity into two and thus lessen
the liability of the organs to sag out of place. The slight hollow
in the lumbar region, aided by the presence of the psoas muscles
and the lower ribs, forms shelf-like places into which the organs
fit, helping to hold them in place.

Several careful studies have been made to find what degree of
obliquity of the pelvis is best. The line between the two-hip joints
is called the principal diameter of the pelvis and the line from the
crest of the pubes to the top of the sacrum is called the conjugate
diameter. Dr. Lovett has collected the results of several studies

THE UPRIGHT POSITION

249

of pelvic inclination and concludes from them that the normal
position is that seen when the principal diameter is level and the
conjugate diameter makes an angle of 50 or 60 degrees with the
horizontal (Fig. 147). This agrees closely with the conclusions
reached by Dr. Eliza M. Mosher, who studied the. question to find
the inclination that would give the best support for the internal
organs. The obliquity of the pelvis can be measured by an instru-

Fig. 147. — Median section through the pelvis: P, pubes; C, pubic crest; S, sacrum;
S.A., sacral angle; P.S., posterior spine. (Spalteholz.)

ment called a "pelvic obliquemeter," devised by Dr. Mosher, or
obtained by measuring the heights of the pubic crest and posterior
spine from the floor and then finding the angle by mathematical
calculation.

Passing now to a consideration of the upper part of the trunk,
the functioning of the internal organs calls for a vigorously erect
position of the neck and chest. The best posture for the lungs is
one in which the chest can be fully and easily expanded, and this

250 THE UPRIGHT POSITION

calls for a firmly erect thoracic and cervical spine, to furnish a
solid origin for the lifting pull of the scaleni and sternomastoids
and to otherwise favor the elevation of the upper ribs. The same
position is also necessary to hold up the diaphragm and the stom-
ach and liver, enabling these organs to function normally themselves
and not sag down on the structures below them.

The slight convexity that is normally present in the thoracic
spine is a part of the primitive arch that is probably desirable to
afford space for the heart and lungs. Because of the small degree
of flexibility in this part of the spine, the tendency of the muscles
to become tendinous with age and the constant force of gravitation,
it is not likely to be made too straight.

To summarize briefly we may say that the ideal standing position
is one in which all the body segments, from head to ankles, form
an approximately straight line, which is inclined forward from the
ankles just enough to bring the weight on the balls of the feet;
pelvis inclined about 60 degrees; lumbar spine slightly concave
and abdominal wall slightly convex; thoracic spine well extended
and chest and head held high.

To maintain the ideal standing position it is essential to have:

1. A normal skeleton, including strong and normally shaped bones
and ligaments.

2. Strong and symmetrical muscles.

3. Nerve centers trained to hold the body in ideal position, under
the guidance of the muscular sense and the sense of equilibrium.

The importance of strong and symmetrically developed muscles
in the maintenance of good posture cannot be insisted upon too
strongly. The body cannot be balanced in erect position without
muscular assistance. The ever-present and unavoidable force of
gravitation is always tending to deepen the normal curves of the
spine and upset the delicate poise of the framework. No one who
lacks the power to hold himself vigorously erect can be expected
to ever assume ideal posture, to say nothing of holding it habitu-
ally. No matter how perfect the poise, a considerable amount of
muscular force is always used in maintaining it, and the stronger
the muscles the less will be the effort and greater the margin of
strength left for work and play and for the meeting of emergencies.

For this reason sedentary occupations are conducive to bad
posture and all persons who engage in them are especially in need
of exercises for muscular development; any activity or manner of
living that involves vigorous muscular movement is conducive to
good posture. Games, plays, and dances, entered into with vim
and enthusiasm are for this reason especially good for posture,
particularly if they involve frequent stretching of the body to its
full height.

THE UPRIGHT POSITION

251

No matter how strong one may be, a certain amount of fatigue
will always bring poor posture. Work requiring fixed positions,
such as writing and drawing, lead quickly to fatigue and are there-
fore bad for posture, no matter how good the posture in which
they begin. We all naturally avoid the fatigue caused in this way
by varying our attitudes in standing, sitting, working and playing
when we can, and the experience should teach us not to require
children to sit still too much or too long at a time. It is by varying
their attitudes more that post-
men and policemen are able to
have better postures as a class
than clerks, book-keepers and
teamsters . Children usually have
-good postures until they have
been in school for two or three

Fig. 148. — The ideal standing posi-
tion. From a chart issued by the
American Posture League.

Fig. 149. — Miss Bancroft's "window-
pole test" for posture. (Photo by Ethel
Perrin.)

years and have been taught to sit still. When the difficulty is one
of fatigue and muscular strength rather than of coordination, as it
frequently is with young children, formal posture training is less
useful than romping plays and games.

Training of the nerve centers to hold the body in ideal position
can only be secured through practice in standing and sitting, but
most normal children get this training and acquire ideal posture

252 THE UPRIGHT POSITION

when they first learn to stand and walk, without any formal train-
ing. Any child is apt to assume the best posture at this time
because it is the only one in which one can easily keep the balance.
Miss Bancroft found by testing 150,000 children of the Brooklyn
schools that those of the first two or three grades stand well; most
of them have the curves normal. From the third grade on the
curves deepen from year to year, evidently as a result of unfavor-
able conditions and work, at school and at home.

When we wish to train a child to assume the ideal posture and
maintain it habitually we need his interest and full cooperation,
something it is not always easy to get. So far has posture training
failed at times to be interesting to children that it has often
merited Dr. Fitz's description of it as a "nerve-racking and soul-
destroying drill." Among recently devised plans to interest both
teachers and children in posture Miss Bancroft's "triple test" should
be mentioned.

In the first part of the triple test the pupils are asked to assume
the ideal posture, and those who can do it acceptably are left to
try the second test while those who fail go to their seats. This
test has been called the " window pole test" because it was suggested
that inexperienced teachers can be helped to make the test by
having each pupil stand beside a vertical rod for comparison.

In the second part of the test the pupils who passed the first
part march in single file in view of the teacher, and all who cannot
keep the ideal posture through four or five minutes of marching
are eliminated.

In the third part those remaining are given a few gymnastic
movements, such as "neck firm" and "stretch arms upward," and
all who can hold good posture while performing these movements
are said to pass the triple test.

Pupils who pass the test are placed apart in the gymnastic period
and may be excused from short posture drills given the other pupils
at intervals between classes. The percentage of those who can
pass the triple test is placed on the blackboard, and on the school
bulletin boards the percentage of different rooms is shown. Com-
petition is also carried on between different schools, especially
between like grades.

For some time there has been a discussion as to whether it is
better to have pupils assume erect standing position as vigorously
as possible, to develop the muscles and stretch shortened tissues,
with resting positions between, or to have them assume a position
less vigorous and maintain it through the whole gymnastic period.
The latter plan has been gaining ground and is now apparently in
a way to entirely supersede the other. The idea of a vigorous cor-
rective exercise is sound, but the practice of resting positions that

THE UPRIGHT POSITION

253

are not standardized nor criticized seems to lead to bad habits
(compare Figs. 149 and 153).
Postures and outlines of the body can be recorded :

1 . By photography.

2. By a pantograph (Fig. 150).

3. By a schematograph.

4. By Lovett's apparatus.

Fig. 150. — Pantograph for tracing outlines of the body: F, foot board for indi-
cating position in which to stand; B, board for holding the paper; L, lever worked
with the foot and bringing paper to pencils; P, pencil arms; T, tracing arms; A,
axis of instrument; C, counterweights; S, supporting standard.

Photography is the most accurate method but it is expensive
and shows too much to be used satisfactorily in routine examina-
tions. The pantograph is less accurate but cheaper to use and is
perhaps accurate enough for all but the most serious cases. The
schematograph is a new instrument put out by the Posture League,
using a reflecting camera and free-hand tracing of the image. Lov-

254

THE UPRIGHT POSITION

ett's apparatus consists of a height standard with a graduated
sliding arm, giving the amount of deviation at any height but not
making a graphic record.

DEFECTS OF POSTURE.

There are several defects of posture common enough and definite
enough to receive attention. They are:

1 . Round shoulders or kyphosis.

2. Hollow back, or lordosis.

3. Flat back.

4. Lateral curvature or scoliosis.

Fig. 151. — The flattened chest seen in kyphosis.

Besides these separate forms we often see a combination of round
shoulders and flat back, which is known as the gorilla type of pos-
ture, and sometimes a combination of round shoulders and hollow
back, called the feeble-minded type, indicating muscular and ner-
vous weakness. Another defect, usually but not always associated
with some of the foregoing, is displacement of the internal organs,

DEFECTS OF POSTURE

255

or visceroptosis. Still another is hernia, in which a portion of the
abdominal contents is forced out through an opening in the
abdominal wall.

Kyphosis or round shoulders is the most common defect of pos-
ture. It consists of a drooping forward of the head and neck and
a consequent increase in the convexity of the normal thoracic
curve of the spine. As its name implies, it is often associated with
abduction of the scapulae, although either defect may occur with-

Fig. 152. — The expanded chest seen in the vigorously erect posture.

out the 'other. It is a part of the function of the scaleni and sterno-
mastoid muscles, as we have seen, to hold up the upper chest and
keep it expanded. The drooping of head and neck that we have in
kyphosis deprives these muscles of their solid points of origin and
allows the sternum and ribs to sink. The exaggeration of the
thoracic curve also depresses the upper ribs. All this flattens the
upper chest, lessens the range of the normal movements of quiet
breathing and leaves some parts of the lungs unused. The heart,
stomach, liver and other organs are crowded and their functions

256 THE UPRIGHT POSITION

hindered. General vitality is lowered and the tendency to lung
diseases markedly increased.

The cause of kyphosis is a failure of the extensor muscles of the
upper spine to hold the head and neck up in erect position. The
posture may become habitual through muscular or nervous weak-
ness or as the result of occupation. Many occupations give rise
to the fault but of all occupations reading probably is responsible
for most cases. Since reading is rapidly becoming a universal

Fig. 153. — Bad posture due to reading with the book held too low.
(Photo by American Posture League.)

habit among civilized people, its causing kyphosis is a serious
menace to racial vigor. How and why does it have this bad effect
on posture ?

When one sits erect and reads from a page at the height of the
eyes he is not very likely to acquire round shoulders, although the
fixed position of the head leads in time to fatigue of the neck
muscles and this in turn to a drooping posture; but if the head is
held in good position the tendency to fatigue is not marked unless

DEFECTS OF POSTURE

257

the muscles are especially weak. The drooped position is brought
about quickly because the effort to hold the arms and book up to
where the book ought to be very soon becomes uncomfortable and
we let the book drop, and then we have to take a position of round
shoulders to see the page (Fig. 153). What is quite as important,
chairs do not fit the curves of the spine so as to make it easy to sit
in good position; practically all chairs now in use compel one to
assume the primitive arch of the quadruped spine in order to rest
in them with any degree of comfort.

* AH

* .— ^3ftj£.

"V"

■

■r If

m »

Fig. 154.-

-Good posture seen when the book is held up.
American Posture League.)

(Photo by

The best way to prevent the formation of bad habits of posture
in this way is evidently not to stop reading nor to leave the condi-
tions as they are and try to cure the resulting defects by posture
exercises. The only way to get results in this case is to provide
some way to hold the book where it ought to be and reform the
chair.

It may be argued that the muscles of the arms ought to be strong
17

258

THE UPRIGHT POSITION

enough to hold the book up, but the fixed position and the weight
of the arms cause fatigue so promptly that the plan is not likely
to succeed with those who read for hours at a time. With a good
chair to help iu sitting erect a good position of the book may be
maintained for a short time, and this is especially true of the read-
ing of newspapers and magazines.

Although man is still enough of a quadruped to prefer to rest
for many hours of the day with spine in the shape of the primitive
arch, it is reasonable that chairs to be used for reading and working
should support the trunk in the normal position it has in standing.
If it is more economical of muscular force and better for the inter-

Fig. 155. — The car seat designed by the American Posture League.

nal organs to have the trunk in the position we have called the ideal
one for standing, the same is true of sitting. The Western races
have by the adoption of the chair improved upon the ancient and
Oriental custom of sitting cross-legged on the 'floor, and there is
good reason why they should now make chairs to fit the normal
position of the human trunk rather than that of the orang-outang.
The work of the American Posture League is of interest here.
The league proposes to secure the manufacture of shoes, clothing
and furniture that will be a help rather than a hindrance in main-
taining ideal posture. They have already designed and placed on
the marked shoes, corsets and waists, car seats, school seats and
desks and an inexpensive bookholder for use on the school desk.

DEFECTS OF POSTURE 259

Intelligent people should become interested in preventive measures
of this kind, for manufacturers of furniture and clothing are quick
to respond to public demand and will make better chairs, etc., as
fast as there is a sale for them.

The best single corrective exercise for kyphosis is the "arch
flexion" of Swedish gymnastics. It is wrongly named, for it is not
a flexion. It is the exact reversal of the defect it is intended to
remedy. The head, neck and upper thoracic spine are moved
upward and backward as far as possible, with the chin held down.
It is made more effective by taking a deep breath at the same time.
The advantage of holding the chin down is that the ligament of
the neck aids in holding the spine up where it should be if kept
taut by not letting the head rock backward.

This exercise is apt to be difficult for beginners to coordinate
because it involves the strong contraction of the splenius and upper
portion of the erector spina? group without any increased action of
the extensors of the lumbar spine — an unusual movement. It is
often helpful to take it while sitting in a suitable chair or with a
firm support against the back at the level of the scapulae, as this
simplifies the problem of coordination and makes it possible to
extend the upper spine with more force. The Swedes combine the
arch flexion with various arm positions, "neck firm" being the best,
especially when there is habitual abduction of the scapulae.

Lordosis, or excessive lumbar curvature, may be due to weakness
of the abdominal muscles or to too great an inclination of the pelvis.
Paralysis or pronounced weakness of the abdominal muscles results
in a shortening of their antagonists — the extensors of the lumbar
spine — and this deepens the curve. If the pelvis tips too far for-
ward the top of the sacrum is inclined too far and this makes the
lower lumbar vertebrae start forward instead of nearly upward as
they should, with the consequence that a deep and long lumbar
curve occurs before the spine can attain an upright position. Too
small a sacral angle may cause the same thing.

An excessive inclination of the pelvis may be due to a faulty
coordination, consisting of a contraction of the flexors of the hip
and a laxness of the hamstring muscles, accompanied usually by
partial flexion of the knees, or it may result from a shortening of
the iliofemoral ligaments. In the latter case the habit of standing
with the toes turned out increases the fault by increasing the
tension on the short ligaments.

The harm done by lordosis is a lessening of the supporting power
of the spine, causing in weak subjects inability to stand much on
the feet, and a tendency to bring on a compensating kyphosis.

As preventive measures complete extension of the knees in stand-
ing, pointing the toes straight forward, and general abdominal

260 THE UPRIGHT POSITION

exercise are most important. Corrective measures vary, depend-
ing on which of the causes is responsible for the fault.

When the position of the pelvis is not at fault the problem is to
devise an exercise that will strengthen and shorten the abdominal
muscles and stretch the erector spinse. For such cases Schatz and
Berggren both describe an exercise in which the subject lies on the
back with the hips flexed until the feet are near the face; in this
position the feet are moved forward and back through a distance
of about a yard, the abdominal muscles working to bring the feet

Fig. 156. — Tracings made with pantograph, showing normal posture, lordosis and
flat back: A, normal; B and C, lordosis; D and E, flat back.

past the head and the elasticity of the extensors bringing them
back. This keeps the extensors of the spine in an elongated posi-
tion and uses the abdominal muscles mildly in a shortened posi-
tion. If the hips are heavy, they may be supported suitably by a
pillow. It is plain that ordinary abdominal exercises, such as leg
raising from horizontal position and inclination backward from
sitting position, are not suited to cases of lordosis because they use
the abdominal muscles in so elongated a position that the effect
will not be to shorten them, even if it does strengthen them.

When the pelvis is tilted forward too far, with shortening of the

DEFECTS OF POSTURE 261

flexors of the hips and the iliofemoral ligaments and elongation of
the hamstring group, it is plain that the exercise used by Schatz
and Berggren will not remedy the difficulty, for it puts the ham-
strings in an elongated position and does nothing to stretch the
flexors. The inclination backward from sitting position is no better,
for it uses the flexors of the hips in a way that tends to shorten
them and does nothing to shorten the hamstrings. One of the best
exercises for this case is to lie on the back on the plinth and try to
lessen the lumbar curve by pressing it down against the cushion.
This brings the abdominal and hamstring muscles into vigorous
action and uses their force to diminish the lumbar concavity and
stretch the flexors of the hips and the iliofemoral ligaments. The
same exercise can be taken in standing position with the back
against a wall. If taken in a similar way while sitting it will act
on the structures above the pelvis but not on those below it.

Flat back, or straight back, as it is sometimes called, is the absence
of any lumbar curve — the opposite of lordosis. It is a reversion
to the position of the ape and quadruped, whereas lordosis is too
great a departure from it. The extensors of the lumbar spine and
the iliofemoral ligaments are elongated and the pelvis lies flat.

The objections to this fault have been discussed in connection
with our consideration of the characteristic position of the orang-
outang and other apes, namely, less stable positions for the liver
and kidneys, increased tendency for these and other organs to sag
down and press upon the pelvic organs, and the weight of all the
viscera borne too much by the perineal muscles instead of by
the pubic arches and rami.

The fault is due to bad habits of sitting, together with a general
laxness of the ligaments that is characteristic of certain individuals.
Most of us sit with the lumbar curve obliterated often enough
and long enough to acquire the defect if the iliofemoral ligaments
did not tip the pelvis into correct position as soon as we stand up ;
when the ligaments are lax the habit is easily formed.

Correction requires the learning of a proper coordination of the
muscles concerned. Since the iliofemoral ligaments will not hold
the pelvis in position, the flexors of the hip, acting with the erector
spinse, must be taught to do it. The subject should incline the trunk
far forward and raise it slowly, being sure to overextend the spine
in the lumbar region. This will train the flexors of the hip to keep
the pelvis from tipping too far backward. Inclining backward not
more than 30 degrees from sitting position should help in the same
way. The hamstring muscles are apt to be somewhat shortened
and bending trunk far forward will aid in elongating them.

Scoliosis or lateral curvature of the spine is a deviation of the
spine sideward from a straight vertical line. The presence of rota-

262

THE UPRIGHT POSITION

tion, which has been explained in connection with movements of
the trunk, is an important feature and a source of much difficulty
in the correction of scoliosis.

Lateral curvature lessens the supporting power of the spine,
distorts the body cavities and thus interferes with the internal
organs, and in advanced cases produces pressure on the spinal
nerves, causing pain and paralysis.

It may be caused by unequal heights of the two sides of the
pelvis, by lack of strength or symmetry of the muscles of the trunk
or by habit due to occupation.

Fig. 157. — Scoliosis.

If the two sides of the pelvis are of unequal height the top of the
sacrum is not level, the lower lumbar vertebra? start upward in an
oblique direction, and this necessitates a lateral curve to maintain
balance. The slant of the pelvis may be due to unequal length of
the lower limbs, to a flat-foot or a habit of standing with one knee
not fully extended.

Cases of lateral curvature are so varied and complications are
so many that correction is largely an individual matter. A plan
suggested by Roth and called by him the use of " keynote" positions,
illustrates the character of the work for the correction of mild
cases. In many of these mild cases the subject has sufficient mus-

DEFECTS OF POSTURE

263

cular strength to easily straighten the curve but is not able to bring
the right muscles into action to do it. By taking a certain gym-
nastic position that fits the case, such as pushing the right arm
upward and the left arm sideward, he corrects the curvature, the
row of spinous processes being for the time perfectly straight and
vertical. Such a position, which must be found separately for each
individual case, is the "keynote" position. The subject practises
this movement many times in each lesson and each time that he
returns his arms to the normal position at the sides he does it
slowly and tries to retain the spine in its straightened position as

Fig. 158. — Straightening a lateral curve by use of a keynote position.

he does so. Gradually he gains the right muscular sense of the
position and becomes able to assume the normal straight position
at will.

In later stages the bones and ligaments become adapted to the
form of the curve, and then correction involves the use of mechan-
ical force to make the spine flexible again along with development
of muscular power and nervous control. An interesting example
of this use of force is suspension of the subject by the head, making
the force of gravitation help in correcting a fault it did much to
cause.

The stomach and liver are attached to the under surface of the
diaphragm and the other abdominal organs to the posterior wall

264 THE UPRIGHT POSITION

by folds of membrane called ligaments. They are not true liga-
ments, composed of strong fibrous tissue like those that hold the
bones in place, but are folds of the peritoneum, a delicate mem-
brane that covers the organs. They are not sufficient to hold the
organs in place. The outer surfaces of the stomach, liver, spleen
and kidneys fit into shallow shelf-like depressions in the body wall
that help to keep them in place when the posture is normal, yet
these are of little value unless the abdominal wall maintains a
constant pressure upon them on the front and sides.

This elastic pressure of the abdominal wall has been referred to
in the study of quiet breathing, the unconscious expulsion of the
breath requiring enough elastic force to press in upon the internal
organs and push the diaphragm upward. Normal circulation of the
blood also requires constant tension on the contents of the abdomen
to prevent the weight of the blood from distending the veins there.

To furnish sufficient elastic tension the four abdominal muscles —
the rectus, internal and external oblique and transversalis — must
be thick and strong and must possess considerable tone. Such a
condition is developed only by regular and fairly vigorous abdominal
exercise.)

In the upright position gravity tends to flex the spine, giving
continual work for the extensor muscles but none for the abdom-
inal group. We all frequently stoop forward, as in fastening a shoe
or picking up an object from the floor, again using the extensor
muscles, but we never do this in such a way as to bring in the
abdominal muscles. The upright position and sedentary life leave
the abdominal muscles without adequate exercise to a greater
extent, probably, than any other muscle group. The result is
further aggravated by the use of corsets and by the distention of
the abdomen in certain diseases and in child-bearing.

When a certain degree of weakness of the abdominal wall is
reached by failure to develop its muscles the organs within begin
to sag. The "gorilla type" of posture with its flat back and droop-
ing chest favors it. Not only are the heavier organs — liver and
stomach — displaced downward but the spleen, kidneys, pancreas,
and transverse colon stretch their supports and move down. Every
organ that sags out of place of course crowds another. In extreme
cases organs that belong in the uppermost part of the abdomen
come to lie in the pelvic region, their weight supported by the
pelvic organs and by the sagging abdominal wall, which protrudes
conspicuously.

Unless the abdominal muscles are diseased, careful exercise of
such a nature as we have described in the chapter on movement
of the trunk is of great benefit, even in late cases. The work must
be carefully suited to the strength of the individual and is often

DEFECTS OF POSTURE

265

taken while lying with the head lowered, so as to make gravity
assist in the return of the organs to place. Movements that bring
the lower parts of the abdominal wall into contraction first and most
strongly are of course to be preferred, and for this reason leg-raising
is better than trunk-raising. Prevention being always better and
cheaper than cure, ptosis of the viscera, as this sagging displace-
ment is called, should be warded off by an active life, vigorous
plays and games being the very best form of exercise for normal
development of the abdominal muscles. School and college gym-
nastics should be so chosen as to provide a goodly portion of work
for these much neglected muscles.

Fig. 159. — Tracings showing sagging abdomen with indication of ptosis: A, normal
outline ; B and C, weak abdominal walls with apparent sagging of the vi scera.

Hernia, or rupture, is a protrusion of some abdominal structure
through an opening in the abdominal wall. The immediate cause
is usually either a fall or other accident or some sudden and vio-
lent contraction of the abdominal muscles, such as suddenly rising
from lying to sitting position or a violent fit of coughing, subjecting
the abdominal contents to great pressure. Sometimes it occurs
without any such occasion being noticed.

The real cause of hernia is the same as that of ptosis — weakness
of the abdominal wall. Even a moderate contraction of the abdom-

266 THE UPRIGHT POSITION

inal muscles produces a considerable pressure within and this is
transmitted in all directions by the soft and flexible organs, bringing
it to bear against any weak point. The weight of the sagging organs
also causes pressure that tends to dilate and rupture any weak
place.

The most common form of hernia is inguinal hernia, which is the
forcing of a loop of intestine or other structure into or through
the inguinal canal. This is a small opening in the region of the groin
through which passes the spermatic cord in the male and the round
ligament of the uterus in the female. The canal enters the abdom-
inal wall just below the transversalis muscle, passes down beneath
the internal oblique to its lower edge — about an inch and a half
and then opens outward through a slit in the external oblique
(Figs. 124, 125 and 142). The canal is normally no larger than
the structures that pass through it, but it is sometimes dilated by
pressure from within when the wall is weak. When the outer end
of the canal is dilated it forms a circular opening through the exter-
nal oblique called the external inguinal ring. After the protrusion
has subsided this ring can be easily felt with the end of the finger —
a fact that is useful in diagnosis of hernia. The size of the ring
may vary from that of a pea to that of a silver quarter.

A common method of treatment of hernia is to wear a truss or
small pad over the inguinal canal to prevent recurrence of the
hernia. If it does not recur the ring tends to shrink and finally
disappear unless the wall is so weak that internal pressure easily
dilates it.

Contraction of the external oblique closes the canal as a
lengthwise pull closes a buttonhole. This prevents a hernia while
the muscle is in contraction. In cases of hernia particularly and
in all cases of weak abdominal wall, abdominal exercise not bring-
ing the oblique muscles into action should be avoided, unless the
external ring is protected by a good truss or by the hand. Direct
flexion of the trunk by raising the head and shoulders from lying
position is risky because it begins with isolated action of the rectus.
Combinations of flexion and twisting away from the side of the
hernia are better.

In some young children and in some women who have borne
children the abdominal wall is weak near the umbilicus, with ten-
dency to hernia at that point. Children sometimes acquire an
umbilical hernia by a violent fit of crying or coughing.

Hernia is another instance of the value of preventive measures.
With strong and well-controlled abdominal muscles it is rare.
Along with ptosis of the viscera and other faults of posture it is a
penalty for leading a sedentary life.

PART V.

GENERAL KINESIOLOGY.

CHAPTER XIV.
TEAM WORK AMONG MUSCLES.

In a former chapter we have seen how the nervous system con-
trols muscles, bringing them into action in groups, stimulating
some and inhibiting others, so as to accomplish useful work. We
are now in a position to inquire further into the association of the
muscles, to see more fully what they gain by such association and
how it is accomplished.

It is well to notice first of all that the muscle fiber is the unit of
action rather than the muscle, for, as we have seen, many of the
muscles are masses of fibers grouped together and named without
regard to their action. The trapezius, for example, consists of at
least four separate muscles as far as action is concerned, the deltoid
of three, the pectoralis major of two, while the rhomboid major
and minor and the infraspinatus and teres minor are examples
of muscles usually named and described separately but having no
separate action. Duchenne has shown by electrical stimulation
that the deltoid consists of a great number of muscular units with
different actions. Beevor has shown that the upper part of the pec-
toralis major is an associate of the anterior deltoid and the lower
part an associate of the latissimus. We have seen how the upper
part of the serratus magnus can be brought into action by the
will in any position of the arm, while the lower part never works
unless the humerus is raised to at least an angle of 45 degrees with
the body. Some muscles, on the other hand, like the brachioradialis
and the levator, have no use in parts and always act as a single unit.

W. C. Mackenzie denies all this in a recent book (reference on
page 329) and insists that all the parts of a muscle must act together.
Such a view is a direct denial of the results obtained by Duchenne,
Beevor and other writers.

Students of the complex problems of coordination are agreed
that the objects accomplished by the association of muscles in a
kind of "team work" are strength, speed, and skill, with some
influence also on endurance. Grace and ease of movement are often

268 TEAM WORK AMONG MUSCLES

mentioned as objects to be sought through exercise, but when we
think of it we see that if the muscles work together economically and
accurately so as to secure the highest degree of strength, speed, and
skill that an occasion demands, grace and ease of movement will result
naturally. Grace and ease of movement are therefore rather indica-
tions of a high degree of coordination in the direction of strength,
speed and skill than separate qualities to be sought by other methods.

The simplest form of muscular association to secure strength or
power of movement is the same as that seen in a team of horses
hitched to a wagon or two locomotives coupled to a train of cars.
Any two muscle fibers lying side by side, pulling at the same time
in the same direction on the same bony lever join forces in this
way. It is well illustrated by the action of the three parts of the
triceps in extending the elbow. If the long head pulls with a force
of 50 pounds, the outer head with a force of 100 pounds, and the
inner head with a force of 200 pounds, their combined pull on the
olecranon is found by simply adding the separate forces. If we want
to find how much force they exert at the hand we have to make one
simple computation based on the length of the lever arms, using
the sine of the angle of pull when this is other than at a right angle.

It is not possible to have all the muscles that need to be used
together so placed that they will join forces in the simple way we
have just considered. In most cases the muscles associated to
move a lever are attached to it at different points and pull at differ-
ent angles. We see a good example of this in the four flexors of
the elbow, or in the action of the deltoid and the supraspinatus in
elevating the arm. Each one does its part in its place and in its
own way and the strength of the movement is aided by each, per-
haps more effectively than it would if all had to work in exactly
the same manner. When we wish to find out the total strength
exerted by the combined pull of the four elbow flexors we must
work out the effective pull of each separately, taking into account
leverage and angle of pull, and then add the results. The following
table illustrates fully the plan to be pursued in such computations.
F is the force of contraction, which must be estimated roughly for
each muscle, considering its size, structure, and condition of training;
/ is the power arm of the lever and L the weight arm, measured on
a skeleton, and 6- is the sine of this angle, found in the table on p. 39;
E is the effective pull or lift at the hand, 12 inches from the elbow,
computed according to the formula given on page 36.

Muscles.

Biceps
Brachialis
Brach. rad.
Pron. teres

400

1.5

0.99619

49.8

200

0.98481

16.4

150

0.24202

38.4

0.17365

5.4

110.0

TEAM WORK AMONG MUSCLES 269

If one is trying to find practically and accurately the strength
of any group of muscles it can be done directly with a suitable
dynamometer. The object of a computation like the above is
rather to get acquainted with the manner of association of the
muscles composing a group. It is evident from the table that if
we judge of the effect of a muscle by its size alone, as one is apt to
do, we are likely to be wide of the mark, for the effective pull
depends not only on the direct power of the muscle but equally
upon its leverage and angle of pull. The brachioradialis, for ex-
ample, while relatively small, has the advantage of an exceptionally
long power arm, and its origin up the condyloid ridge gives it a
considerable angle of pull, with the result that it is very effective
as regards strength of movement.

A third kind of association among muscles for the purpose of
securing strength of movement is the use of one muscle to prevent
one of the two movements another muscle can produce, in order
that its force shall all be utilized in the desired direction. A good
example of this kind is the action of the trapezius and lower ser-
ratus in taking a deep breath. The pectoralis minor is the muscle
whose pull is needed in deep breathing, but its action will rotate
the scapula downward rather than lift the ribs unless that bone is
held firm by other muscles. The serratus and trapezius hold it
immovable or even rotate it upward, thus giving the pectoralis
minor the best possible chance to aid in the breathing. Another
example of this kind is the action of the upper serratus and pectoralis
minor when the triceps is contracted to strike a blow with the fist.
When the fist strikes, the action of the triceps will push the scapula
back and the blow will have little force unless support is given;
the two abductors of the scapula hold that bone firmly forward
and then the whole force of the triceps is utilized for the blow.
Still another example is the action of the triceps in all efforts at
strong supination of the forearm; its use is to prevent the elbow
from being flexed by the contraction of the biceps, so that the full
force of the latter muscle can be utilized by supination.

This kind of association among muscles is exceedingly common,
in fact, every contraction that is made with any considerable vigor
needs to be supported in this way by the action of other muscles,
because every muscle pulls as strongly upon its origin as it does
upon its insertion, and the bone that serves as origin must be held
firmly in place if the force is to be utilized to do what is intended.
This has led to a classification of acting muscles into moving
muscles and supporting muscles, the former producing the movement
and the latter affording the former a solid point of origin. The
fulcrum on which the lever turns must also be made firm if the
movement is to be effective, and the need in both cases increases

270

TEAM WORK AMONG MUSCLES

with the force of contraction of the moving muscles. A good ex-
ample to show this mode of action is seen in opening a table drawer.
One hooks his fingers into the handle of the drawer and if it opens
easily enough the contraction of the flexors of the fingers is suffi-
cient. If it works a little harder the flexors of the elbow contract
to hold the bones of the forearm up so that the flexors of the fin-
gers may have a firm origin. If still more force is needed the latissi-
mus and teres major spring into action to support the humerus
and the rhomboid to hold the scapula. To make a strong pull one
pushes against the table with the other arm and brings the exten-
sors of the trunk into action, and finally, if this does not suffice,

Fig. 160. — Combined action of the biceps and triceps in supination.

the legs are braced and the whole body is converted by muscular
action into a single solid piece in order that the flexors of the fingers
may exert all their power to open the drawer^Another interesting
example of this kind is seen in the suppression of the breathing in
all movements made with greatest force. In many movements of
the upper and lower limbs so much force is required that the trunk
must be made a single solid piece in order to permit the moving
muscles to act upon it with all their power. To accomplish this
we take a deep breath, close the glottis, thus imprisoning the air
in the chest; then when the abdominal muscles are contracted the
solidity of the trunk is increased. This habit of using the air impris-

TEAM WORK AMONG MUSCLES 271

oned in the lungs as a means of making the chest more rigid for
the arm muscles to work upon is a natural one and the coordina-
tion is inherited. It may be a source of danger to persons with
weak lungs, making it advisable for them to avoid severe effort.

The action of the so-called "supporting muscles" differs from
that of the moving muscles in being largely static; they perform
no external work although they consume tissue and give off waste
products just as moving muscles do. Although they help to fatigue
the system and are necessary to the work, the force of these con-
tractions cannot be added to that of the moving muscles to find
the total force of pull. The whole body working in this way can
pull upon the table drawer no more strongly than the flexors of
the fingers can do; they simply enable the flexors of the fingers
to do their utmost. Grace and ease of movement depend much
on the accurate coordination of the supporting muscles; unskilled
performers are apt to hold the body more rigid than is necessary,
making the movement appear stiff and awkward. Only a great
amount of practice can give this needed coordination and made the
movement easy and graceful. For this reason those who stand,
walk, and dance much are apt to be considered graceful persons,
although in movements which they do not perform in public, such
as swimming, throwing, or running, they may be very awkward. |

There are many movements in which the arm, lower limb, or
even the whole body may take part as a system of levers instead
of a series of separate levers, and such conditions enable distant
muscles to help and to transfer their force to levers upon which they
usually have no effect. The act of pushing against a wall with
the arms half-flexed will serve as an example. To make it more
definite, assume the position with the elbows pointing horizontally
sideward. Here the upper arm and forearm,* instead of acting as
separate levers, as they commonly do, are changed by the fixed
position of the hand into a lever system acting in unison. Any
force that extends the elbow also moves the humerus forward, and
any force that moves the humerus forward necessarily acts upon
the elbow to extend it. When, therefore, the pectoralis major
contracts in this exercise it acts for the time as an extensor of the
elbow, and when the triceps extends the elbow it also acts to swing
the humerus forward and extend the wrist. In the pull in rowing
we have another example of the same kind. The elbow of the rower
cannot be flexed without depressing the humerus and the humerus
cannot be depressed without flexing the elbow; the latissimus and the
teres major could produce flexion of the elbow in this position even
if the flexors of that joint were paralyzed; normally they assist the
flexors in this movement while the flexors assist them. The lower
limb works in this way in climbing, jumping, bicycling, and in many

272 TEAM WORK AMONG MUSCLES

other cases, and the arm in pushing, pulling, climbing, rowing, and
in all similar movements. The only condition needed to convert
the arm into such a system of levers and joints is to have the hand
on a fixed object.

Speed can be secured through association of muscles in two ways.
When the resistance to be overcome in the movement is so great
in relation to the size and strength of the muscle that it will dimin-
ish the rapidity of the muscle's contraction, then any of the kinds
of association for securing greater strength of contraction will add
to the speed. In putting the shot, for example, the object to be
gained is to make the shot move with enough speed while in the
hand so that its momentum will carry it a long distance. The
main difficulty in securing the desired speed of movement is the

Fig. 161. — The arm as a system of levers. Arm flexion and extension in the

leaning position.

great weight of the shot, whose inertia cannot be overcome quickly
enough. Here it is evident that all that is needed to get more
speed is to add to the strength of the movement, both by bringing
into action all the moving muscles that can be made to work to
advantage and by supporting the origins of these muscles effectively.
In such movements as throwing a ball, on the other hand, it is
not the weight of the ball that limits us, but rather the inability
of the moving muscles to contract rapidly enough. We need to add
in some way to the speed with which even an unloaded muscle
will contract. This is done by an association of levers and muscles
such as we see in driving nails with a hammer. The extension
of the elbow by the triceps swings the hammer through a certain
distance in a certain time; depression of the arm by the latissimus

TEAM WORK AMONG MUSCLES

273

and teres major can swing it through the same distance in about
the same time; by using both at once the hammer can be swung
through twice the distance in the time, nearly doubling the speed
and momentum of the hammer. The body acts to add to the speed
of the arm in throwing in a similar way. While the arm is being
carried far back in preparation for the throw the body also inclines
far backward, and as the arm swings forward the body swings
forward too, so that, the hand carrying the ball travels six or seven

Fig. 162. — Association of anterior deltoid and biceps group in lifting: B, biceps;
BR, brachioradialis; A, anterior deltoid.

feet in the time it could move through four feet if the arm had to
act alone. The same increase of speed is gained by the united
action of the deltoid and the lower serratus in raising the arm, and
that of the triceps, upper serratus, and pectoralis major in striking
a blow with the fist.

There is an interesting relation between the action of supporting
muscles, discussed above, and the case we are considering now.
The upper serratus supports the scapula in striking a blow with
18

274 . TEAM WORK AMONG MUSCLES

the fist so that the action of the triceps niay not lose force by a
loose origin; the serratus, assisted by the rotators of the trunk can
push the scapula forward and thus increase the range and speed of
the blow. The anterior deltoid can hold the humerus from swing-
ing backward while the biceps group flexes the elbow in lifting,
but if the deltoid shortens while the elbow flexes the speed of the
lift is doubled.

Unlike strength and speed, skill depends entirely on muscular
control. Skill implies accuracy of movement, which is the suiting
of the movement to a purpose, and also economy of force, which
involves the use of the right muscles at the right time with the right
amount of energy. When we say that an exercise was skilfully
done we mean that it did what it was intended to do with the
least possible muscular expenditure. From the aesthetic stand-
point such an exercise is graceful.

The first essential in performing a movement skilfully is to use
the right muscles, those that can do the work required most effec-
tively and easily. The selection of the muscles for many of the
most common movements is an inherited instinct, all persons invari-
ably using the same muscles for coughing, sneezing, walking, run-
ning, jumping, and all the so-called "natural movements." In the
case of racially new movements the coordination is developed by
practice.

The next essential in skill is the use of these muscles with the
right amount of force. Everything depends upon the utmost
accuracy in this control of relative forces. When one undertakes,
for example, to drink a glass of water, too strong use of the deltoid
will toss the water above the head, too strong use of the pronators
will empty it on the floor, too strong use of the elbow flexors will
strike the glass against the face, etc. By varying the strength of
the stimulus that the nervous system sends to each muscle it may
be made to act with any desired force, from its maximum strength
to zero. Every one is familiar with this fact by practical experience.
We habitually grip a door-knob with a force of several pounds but
we just as readily handle eggs with a much milder hold. The way
in which the nervous system controls the force of muscular action
is still a matter of dispute, two theories being held to explain it.

The older theory assumes that every muscle fiber responds to a
mild stimulus by a mild contraction and to a stronger stimulus by
a stronger contraction. It assumes that all the muscle fibers that
compose a muscle act when it contracts either mildly or strongly,
each one responding to the stimulus given by the nervous system
according to the force of the stimulus.

The newer theory claims that each muscle fiber acts with all
its power if it acts at all. Heart muscle has been known to act in

TEAM WORK AMONG MUSCLES 275

this way for a long time, and now many physiologists are coming
to believe that the principle is also true of voluntary muscle fibers
and of neurones. Our ability to vary the strength of muscular
contractions at will is explained on the assumption that some
fibers are able to respond to a slight stimulus while others require
a stronger one. It explains the increase of contraction that results
from an increased stimulus by saying that with a slight stimulus
only a few of the fibers of the muscle respond, these few contracting
with all their force while the others are idle ; with each increase in
stimulus more muscle fibers are brought into action, giving the
increased force. This is not the place to go into the full discussion
of this interesting question.

Whether the newer view is true of muscle fibers or not, it is at
any rate true of muscles. For example, we might naturally sup-
pose that in flexion of the elbow all the four flexors act all the time,
no matter how strong the movement or how mild, but this is not
the case. The biceps, as stated by Beevor, begins to act when
there is a resistance of four ounces if the arm is in supination, but
in a position of complete pronation it does not act until the resis-
tance is at least four pounds. In many cases it is not difficult to
observe that the moving muscles and still more emphatically the
supporting muscles come into action one after another as the force
of the movement is increased.

The correct timing of the action of the various muscles taking
part in an exercise is another essential for skilful movement, for
even if accuracy could be secured without paying attention to the
time that the different muscles begin and end their action it would
unquestionably be economical to have their action accurately
timed. Awkwardness in the performance of new movements usually
consists of a failure to rightly control the force and time of
the action. The manner in which the nervous system controls
the muscles so as to bring each one into action with exactly the
right force and at exactly the right time has been explained in
Chapter III.

Stated again briefly, to apply especially to the point in mind,
every contraction of a muscle stimulates sensory nerve endings in
that muscle, giving rise to nervous impulses that go to the central
nervous system and there do one or both of two things: they give
us a sensation of the state of action of the muscles, or they serve
as a signal for other muscles to begin, change the force of contrac-
tion, or stop. Usually in practising new movements all of this
takes place rapidly, although the sensations are not very definite,
but soon all sense of details is lost and the incoming impulses from
the muscles and joints merely serve to guide the action of the
muscles, giving what we call a reflex movement.

276 TEAM WORK AMONG MUSCLES

The skilful performance of a movement often requires the use
of muscles to guide the direction of it, besides those that move
it and support it. Such additional muscles are called guiding or
steadying muscles. They are especially needed in such exercises
as throwing, shooting, fencing, kicking a football, and others of
similar kind. These muscles must also be selected, stimulated in
just the right degree, and accurately timed by the controlling
mechanisms of the nervous system.

Skilful action often requires also the use of antagonistic muscles.
When a class of pupils is commanded "Fling arms sideward" it is
expected of them that they will move their arms rapidly to hori-
zontal position and stop them in exact position. In certain strokes
used in tennis, croquet, and other games it is necessary to make
a quick and strong movement and then stop or recoil. In all of
these cases, unless the muscles antagonistic to the movement were
brought into action at a certain time the momentum of the move-
ment would be too great to permit of its being rightly performed.
Two sets of muscles standing in the relation of the antagonists of
one another are usually what we have for guiding muscles, as in
shooting.

Coordination may sometimes favor endurance by shifting differ-
ent muscles into action in alternation. In sitting or standing,
fatigue is lessened and endurance increased by varying the atti-
tude. Walking and other exercise can often be modified in a
similar way so as to bring the strongest work on different muscles
in turn.

In all slow movements where accuracy and steadiness is needed,
as in writing, playing a musical instrument, and similar cases, the
antagonists contract along with the principal movers. If there is
strong resistance or if the movement is to be made quickly the
antagonists do not contract and in many cases are inhibited, as
shown by the investigations of Sherrington and Demeney. The
moving muscles may make a quick contraction and then relax
allowing the momentum of the moving part to continue the move-
ment.

QUESTIONS AND EXERCISES.

1. Mention three instances in which two or more muscles aid each other by
pulling on the same lever at practically the same point of insertion, like the separate
parts of the triceps.

2. Mention an exercise in which the deltoid acts as a supporting muscle and
another in which it acts as a "mover;" the same for the serratus; the biceps; the
latissimus.

3. Mention three other instances in which the arm acts as a system of levers, as
in rowing and pushing, rather than as separate levers. .

4. Give three examples of movements in which a muscle works with the deltoid
to secure speed rather than power; three where a muscle works with the deltoid to
secure power rather than speed.

TEAM WORK AMONG MUSCLES 277

5. Mention muscles used in throwing that do not act all at once, and give the
order in which they act.

6. Study the action of wringing a cloth. What muscles act in each arm? Does
the amount of force you can exert in this way depend on the direction of the twist?
Explain why the average person can wring it most effectively when he turns the
right arm over from the body.

7. From the standpoint of this chapter, what is gained when the method of
throwing of the child is abandoned for that of the baseball player?

8. Name the muscles used to guide the movement in striking forward with
a tennis racket against a ball that is over the head; sidewise at the level of the
shoulders; just to the right of the right knee.

9. Mention two exercises in which the infraspinatus assists the deltoid; the biceps;
the latissimus; the subscapularis.

10 J By the use of a hand dynamometer, find how much more you can grip when
the chest is held rigid than when you continue to breath during the test.

CHAPTER XV.
GYMNASTIC MOVEMENTS.

A wooden-legged sailor is quoted as saying that when he had
two good legs he could strike a terrible blow with his fist. He had
learned by his experience one of the basic principles of kinesiology —
that the power of any muscle group depends very much in actual
practice upon how good help it can get from its fellows.

In normal action the associated muscle groups are so controlled
as to give the most effect with the least effort and muscular expendi-
ture. We have studied the action of the muscle groups most
directly concerned in the performance of many of the simplest
gymnastic movements and have also noticed some of the ways in
which muscles are able to help one another. We come now to the
study of the relation of more distant muscle groups to these move-
ments and how the whole body works as a unit to accomplish the
end in view.

Raising Arms Forward. — In raising arms forward all teachers have
noticed that beginners invariably hollow the back and protrude
the abdomen; if there are dumb-bells or other weights in the hands
it is still more marked, requiring repeated corrections of the whole
class and of individuals before all will execute this simplest of move-
ments without losing good position. Waiters carrying trays of
dishes exhibit the same position in an exaggerated form.

The explanation is a matter of balance. With the hands hang-
ing freely at the sides the pupils take an upright position; raising
the arm moves the center of gravity forward so that it is no longer
vertically above the hip-joints. This requires an additional amount
of contraction on the part of the extensor muscles, or a backward
tilt of the trunk to bring its center of gravity over the support
again. The latter way is more saving of energy and so everyone
naturally does it that way. If we want the movement to train a
sense of erect position rather than to get the work done in the
easiest way, we insist that the pupils keep the erect posture.

When the movement is made slowly and without resistance other
than the weight of the arms, we may not be able to feel any con-
traction of the lumbar extensors, but if weights are used or if it is
made quickly the added contraction is plainly felt. With increased
resistance the hamstring muscles and finally the extensors of the

GYMNASTIC MOVEMENTS

279

ankle come into action. When one arm is raised alone the action
of the erector spinse and extensors of the limbs is more marked on
the .opposite side.

Raising Arms Sideward. — In raising arms sideward the weights
of the arms balance each other and little or no associated action
of trunk muscles is needed, but if only one arm is raised the center
of gravity is displaced just as much as in the forward movement.

Fig. 163 Fig. 164

Figs. 155 and 156. — Action of trunk and limbs in raising arms forward. In
Fig. 155 the extensors of trunk, hips and ankles are working; in Fig. 156 their work
is lessened or entirely avoided by shifting the weight farther back.

Here it is the muscles of the opposite side of the trunk that
act — erector spina?, quadratus lumborum, internal and external
oblique — and if the resistance is considerable, the rectus abdominis.
When the resistance to raising one arm is great and the arm is
lifted with force the extensors of hip, knee and ankle of the lifting
side also show increased contraction.
When one arm is raised at any other angle than forward or side-

280 GYMNASTIC MOVEMENTS

ward the trunk muscles also contract and it is always those on the
opposite side of the spinal column from the arm that act — erector
spinse when it is forward, lateral group when it is sideward, abdom-
inal group when it is backward, and opposite intervening groups at
any angle between.

When the arm bearing a weight is raised slowly from the side the
action of the trunk muscles gradually increases up to horizontal
because the angle at which the weight acts is increasing; as the arm
is raised from horizontal to vertical upward the action of the trunk
diminishes again, the weight having no effect to depress the arm
when it is directly upward.

Persons who have short and inelastic pectoral muscles have
great difficulty in raising arms upward and usually hollow the back
by contraction of the erector spinse whenever they try to take the
position, but this is not a matter of gravitation and balance. The
resistance of the opposing muscles keeps on increasing as the arms
are lifted, and since it feels the same as in lifting a weight the
subject jumps at the conclusion that extension of the spine will
help, although in fact it cannot possibly aid in complete elevation
of the arm. In fact, overextension of the spine makes the arms
point upward when they have been raised only part of the way,
so that he appears to have done what was wanted.

Lifting. — The reinforcement of the muscles that raise the arm by
those of the trunk and lower limbs is to be seen in all lifting move-
ments, and the farther away from the body the arms are held and
the heavier the lift, the stronger do these supporting muscles contract.
Notice that the arm acts as a first-class lever, the vertebrae acting
as fulcrum and the trunk muscles pulling down as the arm goes up.

When a weight is to be lifted to a position overhead, as in one
familiar type of weight-liting contests, the trunk is used as far as
possible to aid the arms. Grasping the weight as it lies on the floor,
it is brought to position (Fig. 165), by the action of the extensors
of the trunk and limbs, the flexors of the hand and the trapezius
also acting. To come to the next position, seen in Fig. 166, the
trunk is raised with enough speed to give the weight a quick upward
movement, making it easier for the biceps group to flex the elbow;
then to finish the lift the trunk is quickly flexed to the left, the
side pushing against the elbow and giving the weight another
upward movement. This makes it possible for the triceps and the
arm-raising group to bring the arm to position (Fig. 167) .

Lifting is made easier, as we have seen, by shortening the
weight arm of the lever, and more can be lifted with the elbows
flexed, as in Fig. 162 than .when they are fully extended, as in Figs.
163 and 164. But the extensors of the trunk and limbs are larger and
stronger muscles than those of the arms and it is therefore easier

Fig. 165

Fig. 166

282 GYMNASTIC MOVEMENTS

to lift a weight by starting with these joints flexed and do the work
by extending them instead of by moving the arms. By actual trial
a person lifted 42 kilograms with arms as in Figs. 163 and 164, 68
kgs. in the position of Fig. 162, 120 kgs. in the position of Fig. 6
and 175 kgs. in the position of Fig. 95.

Fig. 167
Figs. 165, 166 and 167. — The three stages of lifting heavy weight in one hand.

Depressing the Arms. — Depression of the arms against resistance
brings the trunk muscles into action in just as vigorous fashion as
we have seen in lifting. Here the action of the arm needs to be
reinforced by the contraction of the trunk muscles that are on the
same side of the spinal column as the arm, the abdominal group
working when the arm is forward and the muscles of the same side
when it is sideward. In depressing the arms forcibly in the forward
position the flexors of the hip also contract.

The action of the trunk muscles in this case can be felt in such

GYMNASTIC MOVEMENTS 283

movements as slow downward movement of the arm while the hand
holds the handle of an overhead pulley or a chest pulley, but it is
most noticeable in quick and forcible movements, like striking
downward with a hammer or dumb-bell. The movements of the
arms in climbing also show this effect on the trunk muscles. In
all these movements the arms act like third-class levers, the fulcrum
being at the spinal column and the trunk muscles acting on the
same side of it as the resistance.

HnHnP

1 5 '■'.

^vHl

.-^-"-•■f

F.t'lfe:

Fig. 168. — Action of trunk and limbs in arm depression: RA, rectus abdominis;
EO, external oblique; RF, rectus femoris; P, pectoral; L, latissimus.

Pushing. — Pushing forward with one or both arms while the body
is erect or nearly so calls the abdominal group and the flexors of the
hips into action to assist the triceps, upper serratus and pectorals.
The extensors of the trunk are fully relaxed in this movement, but
by flexing the trunk and hips, bringing the body into a position more
nearly horizontal and the arms more nearly in line with the trunk

284 GYMNASTIC MOVEMENTS

it is possible to bring the extensors of the hips and spine into action
instead of the flexors. The latter position makes the movement the
same as lifting overhead, with the arm-raising muscles acting and
the reinforcement by the extensors of the trunk and limbs.

Throwing. — Throwing the medicine ball with both hands calls the
muscles of the arms, trunk and limbs into strong action.

Throwing forward from between the knees brings in the elevators
of the arms and extensors of spine, hips and knees. Throwing
forward from over the head uses the arm depressors, flexors of
trunk and hips and extensors of knees and ankles. Pushing it for-
ward from the chest brings in the pushing muscles of the arms,
flexors of spine and hips and extensors of knees and ankles. Throw-
ing it backward over the head uses the elevators of the arms,
extensors of hips and spine, with use of the abdominal muscles to
recover erect position if one leans far back in the throw. A swinging
throw with one arm uses the elbow flexors, pectorals and anterior
deltoid, serratus, and rotators of trunk and hips to the side the
ball goes. A throw backward between the knees uses arm depressors
and flexors of trunk and hips.

Chest Weights. — Exercises on chest weights involve the action of
the muscles of the trunk and lower limbs, which muscles will act
depending chiefly on which side of the body is toward the machine.
Arm movements of all kinds with the face toward the machine
bring into action the extensors of the trunk and hips to resist the
tendency of the arm movement to pull the body toward the machine.
When the back is toward the machine it is the flexors of the trunk
and hips that assist; when the side is toward the machine it is the
muscles of the opposite side. In all positions the weights are
pulling the body toward the machine and the muscles of the oppo-
site side of the body are required to maintain erect position. This
is characteristic of all movements of pulling in a horizontal direc-
tion or nearly so.

Standing Positions. — The fundamental standing position of gym-
nastics and military drill is like the ideal position previously
described except that it is more vigorous. It is considered a cor-
rective exercise for all kinds of faulty postures and the muscles
used in holding the body erect are brought into strong contraction
with the object of increasing their strength and at the same time
stretching tissues that may have been shortened by faulty habits
of posture and work.

The ankle-joints are slightly extended, lifting the heels or at least
keeping all the body weight from resting on them, by action of the
gastrocnemius, soleus, peroneus longus, and the smaller extensors
of the foot. The knees are slightly overextended by contraction of
the triceps of the thigh. The hip-joints are firmly extended by the

GYMNASTIC MOVEMENTS

285

hamstring group. The trunk is held vigorously erect by associated
contraction of the back and abdominal muscles, the upper spine
being extended more forcibly than the lower and the oblique
abdominal muscles used more strongly than the rectus. The arms
are held well back at the sides, shoulders adducted and chin not
raised.

Fig. 169. — Gymnastic
standing position.

Fig. 170.

-Raising one leg sidewnrd while standing on
one foot.

Standing on one foot causes an increased tension of several trunk
muscles because the balance is so unstable. In a vigorous balanc-
ing exercise, such as is used in every lesson of Swedish gymnastics,
the muscles on all sides of the waist are brought into strong con-
traction to hold the trunk firm and immovable.

When the free foot is carried well to the side not only is there
strong contraction of the gluteus medius and minimus of both
sides, as can easily be felt, but the trunk muscles contract to help.

286 GYMNASTIC MOVEMENTS

If the trunk is held erect, as the Swedish system requires (Fig. 97) ,
the trunk muscles on the side of the free limb contract to hold the
spine laterally flexed; if the trunk tips over in line with the free
limb the same muscles act to sustain the weight of the trunk (Fig.
169).

When the free foot is raised toward the rear the hamstring group
acts strongly on the side of the free foot but less strongly than
normal on the supporting side, since the free limb by its weight
helps to keep the supporting hip extended. In order to carry the
leg far back much effort is required, which may bring into action
the gluteus maximus. To carry the leg much to the rear of its
fellow there must be a flexion of the supporting hip to allow the
pelvis to tip forward, as the free hip cannot be but slightly over-
extended in normal subjects. If the trunk is at the same time held
erect it must be accomplished by overextension of the lumbar
spine by vigorous action of the erector spinse; easy to observe either
by feeling or sight.

When the free limb is raised forward or the knee raised forward
with knee flexed the abdominal muscles are not brought into play
as one might expect and as many teachers suppose, because the
hamstring group of the supporting limb is in strong action and
this keeps the pelvis from being tilted forward by the weight of
the raised limb. Indeed, if more force is needed to do this those
same hamstrings can do it by an increased contraction more easily
than the abdominal muscles because they are usually so much
stronger. Attention has already been called to the error so often
made by teachers in giving leg-raising forward for development of
the abdominal muscles. To bring these muscles into action at all
in this movement the limb must be lifted vigorously with flexion
of the pelvis on the trunk and slight flexion of the supporting knee.
This flattens the back, stretches the hamstring muscles and tends
to put the performer in the gorilla type of posture. If the spine is
held strongly extended the effort tends to inhibit the abdominal
muscles, which are antagonists of the extensors of the trunk.
Lifting the flexed knee high up in front is excellent work for the
flexors of the hip, but it cannot be lifted high enough to bring in the
abdominal group without doing more harm than good as long as the
other limb is supporting the weight. If the body is tossed in the
air as in hopping or running, the lifting of tne knee calls the abdom-
inal group into action to support the front of the pelvis.

Sideward Stride. — The sideward stride position to right is taken
by first contracting the left gluteus medius and minimus and the
left erector spinse and quadratus lumborum to raise the right side
of the pelvis and free the right foot from supporting weight; then
abduction of both hip- joints by the gluteus medius and minimus

GYMNASTIC MOVEMENTS 287

of both sides and a relaxation of the trunk muscles contracted at
first to bring the trunk to erect position on the new base. The
sideward stride position braces the body for lateral movements
and lessens any balance problem involved; this is important in
bending sideward, especially when working against resistance, as
in using pulley machines with side toward machine and in wide
side bendings with arms high and a weight in the hands.

In sideward bending of the trunk, which has been described and
explained, the work of the muscles is made greater by raising the
arms, because it raises the center of gravity and hence lengthens
the weight arm of the lever and also because raising the arm puts
a tension on the latissimus, which must be elongated by a side
bending, the tension caused by the arm raising stretching it still
farther and requiring more force to make a complete lateral flexion.

Forward Stride.— The forward stride is executed by partial flexion
of hip and knee on the moving side together with strong contraction
of the abductors and hamstring group of the supporting side and
slight overextension of the lumbar spine by contraction of both
erectors spinse. The inclination of the rear limb tips the pelvis and
necessitates hollowing the back a little unless the iliofemoral liga-
ments are lax. The forward stride position braces the body and
eliminates balance difficulties in exercises of pushing and pulling
and bending forward and backward. It is useful in teaching begin-
ners arch flexions, neck firm and arms upward, the elimination of
the balance problem aiding in the coordination to avoid over-
extension of the lumbar spine. It is not used in inclining trunk
forward from the hips because the inclination of the forward foot
increases the tension on the hamstrings and prevents tilting the
trunk on the hip-joints — the sideward stride being a better starting
position for forward bendings for this reason, unless the nature of
the movement will allow flexion of the forward knee to slacken
the hamstrings. Forward stride position favors twisting the hips
toward the side of the rear foot and hinders it in the opposite direc-
tion, so that where an extensive twisting movement to the left is
wanted, as in throwing and striking with the right arm, the right
foot is placed forward. In twisting trunk to left as a gymnastic
movement, where it is desired to eliminate twisting in the hips,
the left foot is placed forward.

Raising of the arms increases the work of forward bendings of the
trunk by raising the center of gravity and thus lengthening the
weight arm of the lever. The tension that arm raising puts on the
latissimus may or may not affect the work, depending on the form
of the exercise.

In ordinary walking the trunk inclines slightly forward, the incli-
nation increasing with the speed. This throws the weight of the

288 GYMNASTIC MOVEMENTS

trunk on the back muscles and the erector spina? can be readily
felt in contraction, the muscle on the side of the forward foot com-
ing into action with each step. If one inclines the trunk backward,
as one is inclined to do when walking in the dark, so as to feel his
way and avoid stumbling, the abdominal muscles act in a similar
manner.

In a moderate walk the arms seem to swing passively, no action
of the pectoral or latissimus being apparent and the arm seeming
to lag behind as one side and the other swings forward in alterna-
tion. In brisk walking the swing is active and the action of the
muscles can be felt as it swings. The latissimus may act with the
erector spinse and swing the arm.

As shown in Fig. 99 the hips swing forward considerably in alter-
nation, especially in walking with a long stride, but the shoulders
of a graceful walker do not swing nearly so much, and this involves
a twisting of the trunk with each stride, partly brought about by
the swing of the arms and partly by the oblique muscles. The
muscles on the sides of the abdomen seem to be in mild contraction
in vigorous walking, but one would not expect to feel rhythmic
contractions and relaxations, since the external of one side works
as the hip goes forward and the internal of the same side as it
swings back, making the action continuous.

In running we have a more vigorous movement, but during the
time that the weight is supported by one foot (about three-fourths
of the time) the action as regards the arms and trunk is the same as
in walking, with a little greater intensity due to the spring from
the ground and to the shock of alighting. While the body is unsup-
ported there is ordinarily little for the flexors or extensors of the
trunk to do, unless the limbs are raised forward or backward farther
than in the reverse direction. In such a case work is thrown on
the abdominal muscles if they are lifted high up in front and on the
extensors if raised high at the rear.

Charge, Lunge and Fallout. — The forward charge, lunge, and fallout
are gymnastic positions in which the foot is placed forward a long
stride and the forward knee flexed until it is vertically above the
toes. The position puts nearly all the body weight on the flexed
limb, the extensors of the forward hip, knee and ankle being used.
In the fallout the trunk is held in line with the rear limb, which calls
the extensors of the spine into action to sustain its weight. The
lunge and charge are practically alike and differ from the fallout
in holding the trunk erect. This lessens the work of the front limb
and overextends the lumbar spine, since the inclined back limb keeps
the pelvis tilted forward at a large angle. This makes the fallout
preferable for posture training, unless the pupils have flat backs and
need special practice in hollowing the back at the waist line.

Fig. 171

Fig. 172
Figs. 171 and 172.— The sideward lunge and fallout.

290

GYMNASTIC MOVEMENTS

The charge, lunge and fallout are all taken sideward as well as
forward. The action of leg muscles is about the same in all as in
the forward movements. In the sideward movement the free
abduction that is possible in the hip makes it possible to hold the
pelvis level, eliminating the trunk bending that the forward lunge
and charge involve. In the sideward fallout the weight of the
trunk is thrown on the muscles of the upper side. With elevation
of arms and bending toward the flexed limb this position gives
opportunity for strong work of the lateral flexors of the trunk.

The charge, lunge and fallout can also be taken at any angle
between forward and sideward. It should be observed that in these
movements the face and shoulders are always turned in the direction
they had before starting. If the body is turned in the direction
the foot is placed the mechanism will always be like the forward
movement. In the diagonal fallouts the weight is thrown on the
muscles on the side of the trunk that is uppermost.

Fig. 173

Gymnastic Dancing. — Gymnastic dancing includes a great variety
of movements on the feet and involves leaping, poising, hopping

GYMNASTIC MOVEMENTS

291

and bending. It brings into action the extensors of the ankles,
knees, hips and spine strongly and the flexors of the limbs and
trunk moderately, with mild action of the arm-raising muscles.
The abductors of the hip-joints are strongly developed by the
emphasis placed on poising and alighting on one foot.

Fig. 174
Figs. 173 and 174.— Characteristic positions in gymnastic dancing.

Prone Falling. — The prone fall (Swedish) or leaning rest (German)
position, shown in Fig. 130, supports the body by the arms and toes
in nearly horizontal position. The weight pulls down on the head,
requiring action of the extensors of the upper spine to keep it in
position, and tends to make the body sag in the middle, requiring
strong action of the flexors of lumbar spine and hips and slight
action of the extensors of the knees. The action of the arms is the
same as in a typical exercise of pushing. Flexion and extension of
the arms while in the position is strong work for the pushing muscles

292

GYMNASTIC MOVEMENTS

and is done most easily with the fingers pointing somewhat inward,
which turns the elbows out at right angles to the trunk and enables
the whole pectoralis major to work (Fig. 161). The work can be
made easier when desired by allowing the knees to rest on the floor
or by placing the hands on an object above the floor.

Fall Hanging. — The fall hanging (Swedish) or leaning hang
(German) position, shown in Fig. 175, requires work of exactly
the opposite sets of muscles — flexors of neck, extensors of lumbar
spine and hips, and pulling muscles. This, too, can be made lighter
work by increasing the slant of the body.

Fig. 175. — The fall hang or leaning hang position.

Side Falling. — The side falling (Swedish) or side leaning rest
(German) position calls into action the muscles on the lower side
of the body and the upper side of the neck as in the two preceding
exercises. The lateral flexors of the waist region and abductors of
lower limb, which may be assisted by the abductors of the upper
limb, keep the body straight. The triceps and upper serratus do
most of the pushing while several of the muscles about the shoulder
work more mildly to keep the body balanced on the arm.

GYMNASTIC MOVEMENTS 293

Side Holding. — The side holding (Swedish) or side leaning hang
(German) position involves the pulling muscles of the arm, upper
side muscles of neck and lower side of body, as before.

Exercises in which the weight of the body is supported by the
hands, like hanging by the hands from bars or rings (Fig. 77), cross
rest on the parallel bars (Fig. 78), and front rest on the horizontal
bar, do not involve any work of the trunk or lower limbs if one
simply supports his weight the easiest way; but it is usual in those
exercises to adduct the scapulae and to fully extend the spine, hips,
knees and ankles. Most gymnasts know no reason for doing this
except that it is recognized everywhere as "good form;" yet there
is a good reason.

All movements of suspension and of arm depression tend to chest
expansion through the upward pull on the ribs by the pectoral
muscles, unless the movement involves the action of the abdominal
muscles, which hold the ribs down. The vigorous extension of the
upper spine tends itself to expand the chest, and the vigorous exten-
sion of the lower spine brings about an inhibition of the abdom-
inal muscles, lowering their tone below that of the resting condition
and hence interfering to the least possible extent with elevation of
the ribs. Extension of the hips is also good because any flexion
of the hips will require action of the abdominal muscles to hold
the pelvis up.

Strong action of the pectorals always tends to draw the shoulders
forward and the upper spine along with it, and for this reason
exercises of the kind we have just been considering are not consid-
ered good for anyone unless he is able to hold his shoulders back
and spine extended while doing them.

Acrobatic Work or Tumbling. — Elementary acrobatic work or
tumbling brings in strong action of many muscles.

The forward roll begins by completely flexing the lower limbs
and the spine by a lengthening contraction of all the extensor
muscles, and placing the hands firmly on the floor close in front of
the feet. In this position a circle two feet in diameter will nearly
coincide with the back, and the hands and feet will also be on its
circumference (Fig. 176). Now a quick extension of the ankles
throws the whole weight of the body on the hands and the arms
support it momentarily by a forward and upward push; then the
roll continues, first the back of the head touching the mat, then
the neck, back (Fig. 177) and hips in turn, the momentum soon
bringing the feet to the floor again (Fig. 178.) As soon as the
middle of the back comes to the floor the flexors of spine and limbs
must come into action or the weight of the separate parts will
extend them and the movement will finish with the gymnast lying
at full length on his back. The body must be held in complete

294

GYMNASTIC MOVEMENTS

flexion by action of the flexor muscles until the feet come to the
floor again and then the extensors must work in turn, the movement
finishing in standing position. By a strong push by the arms at
the right time the head can be kept from touching the mat.

Fig. 176. — The forward roll. Starting position.

By practice of this simple movement one who is strong enough,
as soon as he has learned the coordination of the push with the
hands, the full flexion of the body and then its full extension, can

Fig. 177. — The forward roll. Midway.

undertake the long or high dive, in which the body is launched into
the air head first by a forcible extension of the limbs, touches the
mat first with the hands, and completes the movement as in the

GYMNASTIC MOVEMENTS

295

forward roll. The muscular action is the same but much more
vigorous, the arms having to sustain more weight to protect the
head from striking too hard and the speed of the movement making
it more difficult to flex the body soon enough.

The front summersault is a variation of the high dive. The gym-
nast springs high into the air and then suddenly flexes his whole
body into the position it takes in the forward roll. To do this in
the air and to do it quickly enough calls for a very sudden and
strong action of the flexor muscles of trunk and limbs, beginning
with a violent downward swing of the arms. The body turns
completely over in the air and at exactly the right time the exten-
sors act and support it in normal position on the feet.

Fig. 178.— The forward roll. The finish.

The baclncard roll reverses the movement of the forward roll.
The body is quickly flexed to the circular position described above
(Fig. 178) and tipped strongly backward to give momentum, with
the hands held back over the shoulders at each side of the head.
The back strikes the mat first and the body rolls (Fig. 177) backward
on to the shoulders, neck and head, the arms pushing backward
and keeping the weight from bearing too heavily on the head. This
stage calls for strong action of the flexors of the entire spine and
limbs, to maintain the flexed position, and strong arm elevation
with flexed elbows to support most of the weight. The arms bear
practically all the weight for a moment and then as the roll con-
tinues the feet come to the mat and the body rises to erect posi-

296 GYMNASTIC MOVEMENTS

tion. It is difficult for beginners to strongly elevate the arms and
strongly flex the trunk and limbs at the same time, but as soon as
this coordination is mastered the backward roll is little harder than
the forward roll.

The backward summersault is a more difficult variation of the
backward roll. The gymnast springs strongly into the air, at the
same time swinging his arms strongly upward and backward and
overextending his spine. As soon as his feet leave the mat the limbs
are strongly and quickly flexed and then the trunk is completely
flexed. If the flexion of limbs and spine can be done quickly enough
the body makes a complete turn in the air and the gymnast alights
on his feet.

The back handspring is a slight variation from the summersault.
The difference is that the jump is not quite so high and the arms
are partly extended as the head is downward, the weight rests
momentarily on the hands and the movement finishes as in the
back roll.

The forward and backward rolls are taken on the parallel bars
with almost the same muscular action as on the mat, and a number
of pleasing variations are there possible. The backward roll is an
especially strong abdominal exercise.

In circling the horizontal bar the gymnast first hangs by his hands,
lifts his weight by flexors of elbow and arm depressors, and then by
flexion of trunk and limbs and still stronger arm depression he
raises his knees over the bar; by this time the trunk is curved and
the center of gravity is so nearly above the shoulder-joint that
further arm depression is possible, sliding the thighs over the bar
to the hips; now the weight is so nearly balanced on the bar that
by flexion of the wrists one can raise the trunk and lower the limbs,
the knees having been extended to aid in the process. As soon as
the center of gravity has been transferred to the side of the bar
where the feet are, the spine can be extended, which brings the body
to the rest position on the bar.

The headstand is begun like the forward roll, but when the hands
have been placed upon the mat the head is extended and placed
on the mat a foot or thereabouts in front of the hands. Using the
head and the hands as the three legs of a stool the gymnast, by
careful extension of his elbows and of his spine, lifts his limbs
vertically into the air. Although much of the body weight must
be borne by the arms, the latter must gradually flex more and more
as the hips and spine extend so as to keep the balance. The exten-
sors of the arms and of the spine and limbs have the work to do
in this exercise, for as soon as the weight is carried far enough back
to call the abdominal muscles into action the balance is lost.

The headspring begins like the headstand. The body weight

GYMNASTIC MOVEMENTS

297

Fig. 179

Fig. 180
Figs. 179 and 180. — The headspring. Start and finish.

298

GYMNASTIC MOVEMENTS

should be balanced on the head and hands with hips fully flexed and
knees nearly straight (Fig. 179). When this position is gained the
elbows should be gradually extended by action of the triceps until
the body begins to fall backward. A sudden and strong extension
of arms, trunk and hips should now be made by use of all the
extensor muscles, projecting the body into the air feet first, in a
direction diagonally upward and backward. If this is followed by
a quick flexion of trunk and limbs the body will turn enough to
come to the mat with head up and feet on the mat, and erect posi-
tion can be gained by use of the extensor muscles again (Fig. 180).

Fig. 181.— The handstand.

The handspring resembles the headspring but is taken with arms
extended up at vertical position beside the head. A run is usually
needed to give the required momentum for turning completely
over. Ending the run by bending completely at the hips and
with the hands on the floor, with a jump as in any running jump

GYMNASTIC MOVEMENTS 299

the body is fully extended with enough momentum to project it
into the air and this is followed by a strong push with the hands.
Until the coordination is learned it is usually necessary to flex the
limbs and spine to gain a position on the feet, but with skill the
finish can be made standing fully erect. The same alternate use of
the flexors and extensors of the trunk and limbs is here combined
with strong work of the arm-raising muscles, triceps, and extensors
of the wrist.

The handstand is begun like the handspring except that it is
taken from standing position without a run and is started slowly
and carefully. With hands on the floor as far apart as the shoulders
and close to the feet, the body is lifted by a spring from the feet
and extension of hips and spine. To get into balance is the main
difficulty here, and to do it the head should be held far back and
neck and spine overexended. The work is practically the same as
that done when one stands on his feet and holds a weight overhead,
the difference being in the lessened action of the extensors of knees
and ankles. (Fig. 181.)

The snap-up or spring from the shoulders starts with the back
on the mat and the limbs and spine flexed as in the midposition
of the backward roll (Fig. 177). When the weight reaches the
point of balance on the hands and shoulders a strong extension of
all the joints is made, finishing as in the headspring. When good
control of the extensors of trunk and limbs has been gained this
can be done with the arms folded.

QUESTIONS AND EXERCISES.

1. Demonstrate the difference between fallout, charge and lunge, and explain
the difference in the action of the trunk muscles.

2. What muscles are brought into action most strongly by balancing across a
horizontal bar, face upward, body and lower limbs in a straight line?

3. Point out the places in the front roll-over where the action changes, one set
of muscles relaxing and another acting instead.

i. Explain how the back roll-over calls for different muscles than front roll-over.

5. In what part of the headspring is the back most used? The abdominal
muscles? The arms? The legs?

6. What muscle groups help in the pull-up and not in the push-up? In the
push-up and not in the pull-up? Which are used alike in both tests? See Figs. 77
and 161.

7. When a pupil is unable to circle the horizontal bar by grasping it with the
hands and putting the feet and limbs up over it, what exercises on pulley machines
will help to prepare him for it? What particular muscle groups are most apt to be
at fault?

8. What muscle groups are most used in the exercises of Figs. 171 and 172?
How does the mechanism differ?

9. Show a dancing position that will develop the right erector spinse; the left
external oblique; the external rotators of the hip.

10. Mention an exercise on the vaulting horse that will develop the abdominal
muscles; the back muscles; the lateral trunk muscles; the arm depressors; the arm
elevators; the biceps; the triceps.

CHAPTER XVI.
PLAYS, GAMES AND SPORTS.

We can class all the bodily movements found here into two main
groups: locomotion and the handling of objects. The handling of
objects involves pushing and pulling, catching and throwing, strik-
ing and kicking. Pushing and pulling have been explained. Catch-
ing involves action of the flexors of the fingers, hands or arms,
together with other movements not definite enough to be described
or explained readily. Throwing, in the general sense in which it is
used here, includes all such movements as tossing, pitching quoits,
bowling, throwing a ball or stone, putting the shot and throwing
the hammer.

Tossing. — Tossing is done by a forward swing of the arm, which
hangs down by the side, the ball or other object being released near
the end of the swing. When the purpose of the play calls for a toss
to a considerable distance the movement is apt to start with one
foot advanced and the trunk and lower limbs somewhat flexed;
as the toss is made there is quick extension of all these joints to add
to the force of the toss. The arm-raising muscles and the exten-
sors of the trunk and lower limbs do the work, the flexors of the
elbow assisting in some cases.

Pitching. — Pitching quoits and bowling employ exactly this form
of toss, with a quick extension of spine, hips, knees and ankles to
add force to the swing of the arm. Bowling requires a little more
power, and this is gained by taking two or three quick running
steps just before the toss is made. Tossing differs from other forms
of throwing in the absence of rotation of the body around a vertical
axis; this makes it milder than the others.

Throwing. — In throwing a ball or stone, the arm movement of
which has been explained in Chapter VI, the problem of the thrower
is to combine accuracy of aim with the greatest possible speed. To
gain the latter the arm movement is reinforced by a forward move-
ment of the body combined with a rotation around a vertical axis.

In preparing to throw, when distance or speed is important, the
foot of the throwing side is placed well back and the body tilted
far back by flexion of the limb, with the opposite arm held forward
in the direction of the throw. In preparing to throw with the right
hand the trunk is turned far toward the right by the rotators of

PLAYS, GAMES AND SPORTS

301

Fig. 182

Fig. 183
Figs. 182 and 183. — Action of the whole body in throwing

302 PLAYS, GAMES AND SPORTS

the spine and by rotating the right hip inward and the left hip
outward. Then, as the arm goes forward the body is inclined quickly
in the same direction by a vigorous contraction of the extensors of
the right hip, knee and ankle and the flexors of the spine, and at
the same time it is swung quickly to left on its vertical axis by the
oblique muscles of the trunk, reinforced by strong action of the
outward rotators of the right hip and inward rotators of the left,
and by a violent backward swing of the left arm. This action of the
body almost doubles the distance the ball travels in the time it is
being moved forward by the arm and consequently nearly doubles
the speed with which it leaves the hand.

A ball is made to curve as it passes through the air by giving it
whirling motion on an axis at right angles to its line of flight, or
nearly so. The rapid rotary movement of the ball causes greater
air friction on the front and one side of it than on the other side,
and this friction acts to turn it slightly out of its course. One can
remember which way it will go by recalling that the side of the ball
that rotates toward the thrower will have least friction with the
air and therefore the ball will turn that way. When the lower side
of the ball spins toward the thrower it will have a "drop" curve;
when the top turns toward the thrower it will have a rising curve
if there is sufficient speed and spin, for of course it takes more air
friction to move a ball upward than it does to turn it any other
way. When the right side of the ball turns toward the thrower it
gives the "inshoot" and the opposite the "out curve." The out
and in curves show a combined motion sideward and downward
which forms a spiral path for a short distance.

The spin that produces the curving of the ball from its path is
given by the manner of releasing the ball from the hand. The
drop and out curves are usually made with the ball held between
the thumb on one side and the fingers on the other, releasing it so
that it will roll off the thumb side of the forefinger by quickly
extending the thumb and thus removing its pressure on the ball.
If this is done while the fingers are in a horizontal position, thumb
upward, the ball will make the drop curve; if the fingers are point-
ing upward, knuckles down, it will give the "out." The inshoot
and rising curve are given by making the ball roll off the ends of
the fingers, the direction of the curve depending, as before, on the
way the hand is turned when the ball is released. A ball released
in the latter way is apt to have more speed and less curve than in
case of the drop and the out curve.

In the game of cricket the act of throwing the ball to the bats-
man is called "bowling" instead of the American term "pitching,"
and the bowler is not allowed to flex or extend his elbow in making
the throw. This, as it is intended, limits the speed and accuracy

PLAYS, GAMES AND SPORTS 303

of the throw but it does not prevent the throwing of curves. Since
the ball must be released while it is moving in the arc of a circle
instead of a straight line it requires a greater degree of skill to throw
with the same accuracy and this puts a limit on the speed one can
attain. The bowler, however, is not required to throw the ball
within so narrow a limit as the pitcher.

Some pitchers are able to throw a very speedy and quickly curv-
ing ball by a snappy and jerky swing of the arm, without much
body movement. They are often very effective for a time, but
experience shows that the man who uses the more widely distrib-
uted movement survives longer.

Pitchers have during the last few years developed the custom of
using a widely swinging preliminary movement of the arms, famil-
iarly called the " wind-up." This was for a time considered as a
mere mannerism of some of the men, persisted in to make them-
selves conspicuous, but it has become almost universal among
pitchers in spite of the general ridicule allotted to it, which argues
its utility. It is light work mixed in with the violent work of
throwing — a practice that is good for the muscles, helping to circu-
late the blood through them in a manner similar to massage.

The essential difference between the throw and the shot-put
arises because the shot is too heavy to handle in the manner of
throwing, the throwing movement is forbidden by the rules, and
the sole object of the sport is to secure the greatest possible dis-
tance, measured from the circle in which the thrower stands to
the place where the shot strikes the ground. Such a purpose and
manner of measurement calls for the precise elevation that will give
the longest put with a certain force. As a consequence the shot-
putter uses more extension of the arm and body and less rotary
movement, although the latter is important.

In preparation for putting the shot with the right arm the athlete
puts the right foot far back, like the thrower, and he flexes his right
limb still more than the thrower, since he must follow the shot with
his hand through as long a path as possible to give it speed. He
usually perfects his balance and gets the right tension on his trunk
and leg muscles by one or two hops on the right foot with trunk
flexed far over sideward to right, left arm and foot extended far
to left to balance the extreme lateral flexion.

As the arm is extended diagonally upward in putting the shot the
abductors of the scapula pull the shoulder forward, the crosswise
direction in which the movement starts being favorable to best
contraction and leverage of the pectoralis major. At the same time
the oblique muscles and rotators of the hip-joints turn the shoul-
ders strongly to left, aided by a violent downward and backward
swing of the left arm, and the extensors of the spine and limbs

304 PLAYS, GAMES AND SPORTS

project the whole body forward and upward. The left limb swings
backward to reinforce the rotation, prevent too much forward
movement and give balance on alighting. At the finish the del-
toid, lower serratus and left erector spinse are doing the most work
in place of the pectoral, upper serratus and right erector spinee,
which were in a position to do most at the beginning. The posture
is now so far forward that the left arm and leg are needed far to the

Fig. 184

rear to prevent falling forward or stepping out of the circle, the
extensors of spine and limbs continuing in action to recover erect
position. As the feet strike the ground in alighting the balance is
apt to be so far forward that the extensors of trunk and right limb
must relax to a certain degree, using a lengthening contraction of
the muscles until the center of gravity of the body is brought
within the base. Notice that while the muscles used in throwing

PLAYS, GAMES AND SPORTS

305

and putting the shot are almost the same the coordination is alto-
gether different, the one putting emphasis on rotation and the
other on extension; the first aiming to give a light object maximum
speed, the other aiming to exert most force in the right direction
against a heavy weight; the first emphasizing accuracy and the
other neglecting accuracy for power and speed.

Throwing the hammer, like the use of the sling by the ancients,
utilizes centrifugal force to a greater extent than other forms of
throwing. The thrower stands in a seven-foot circle and begins

Figs. 184 and 185.

Fig. 185
-Action of the whole body in putting the shot.

the movement by swinging the hammer in a circular direction
about his head, the circle being lower in front of him and higher
behind him. This uses the pectorals, serratus and anterior deltoid
of one side and the trapezius and middle and posterior deltoid of
the other, reinforced by the strongest action of the rotators of the
trunk and hips. The body stoops forward somewhat as the ham-
mer swings forward, enabling the extensors of hips and spine to
help as it swings backward over the shoulder. The arms, which
flex in beginning the first swing or two, remain fully extended after
the hammer has attained speed; the feet are separated and by alter-
20

306 PLAYS, GAMES AND SPORTS

nate flexion and extension the limbs help in the circular movement
of the body and arms. After attaining the most speed that can be
gained in this way the athlete turns his entire body once or twice
by springing from the feet and finally lets go of the hammer at the
end of the backward swing by a specially vigorous extension of the
trunk.

The several forms of throwing, as well as striking and many
movements used in industry, illustrate the fact pointed out by
Dr. Allis that the erect position enables man to use the rotary
movement of the trunk about its vertical axis as one of the most
effective muscular mechanisms. None excel the hammer throw in
exhibiting the utmost power than can be secured by this move-
ment, the action of the arms, trunk and lower limbs being utilized
to full extent when the coordination is mastered.

Striking. — Games and sports employ several distinct forms of
striking. Among them it will be interesting and useful to consider
the use of the hand in volley ball, handball and boxing, the use of
the racket in tennis and of the bat in baseball and cricket.

In the game of volley ball the large light ball must be struck
while it is in the air and batted in an upward direction with the
open palm of one or both hands. It must in most cases be batted
forward and upward; sometimes directly upward and sometimes
sideward and backward. When it is struck with the arms held
above the level of the shoulders it will call into action the triceps
and the. muscles of arm elevation to bat the ball in any direction
but backward, and then the flexors of the elbows may be used in
place of the triceps. When the ball is sent nearly upward or in a
backward direction the arm muscles will be reinforced by the exten-
sors of the trunk and hips; in general it will employ the trunk and
hip muscles of the side toward which the ball goes.

When the ball is struck below the level of the shoulders it requires
action of the flexors of the elbow and the arm-raising muscles; they
are assisted by the extensors of trunk and limbs in the main, as in
lifting. The frequency with which the extensors of the whole
body and arm elevators are used in this game makes it an espe-
cially good one for people engaged in sedentary occupations and
needing moderate exercise for general development and posture.

Handball is a much more strenuous game, played by two and less
often by four players, a tennis ball or other ball of about the same
size being batted against a wall by the open hand. The game
requires much rapid running and dodging to avoid being hit by
the ball and to get into a position to play it. The ball is usually
batted forward by a strong forward swing of the arm. The motion
when the ball is low is much like that seen in a toss, the arm move-
ment being reinforced by the extensors of the trunk and limbs, the

PLAYS, GAMES AND SPORTS 307

trunk bent low to give the strongest blow. When the ball comes
at waist level the rotation of the body is brought into action as in
throwing, and when it is above shoulder level the arm depressors
act with the abdominal muscles and flexors of the hips.

The form of striking used in boxing resembles closely in its gen-
eral mechanism that seen in throwing and putting the shot. The
object is in this case to strike a heavy blow with the closed fist,
usually in a nearly horizontal direction. The arm and body are

Fig. 186. — Action of the whole body in striking with the fist.

not carried so far back in preparation for the blow in boxing as
they are in throwing and shot putting, partly because of necessity
for being ready to dodge or parry a return blow. The importance
of the help the arm receives from the rest of the body is emphasized
by the stress laid by instructors in boxing on the " foot-work." As
the arm shoots forward in the act of striking the abductors of the
scapula draw the shoulder forward and the whole body turns on
its vertical axis by the usual method while the extensors of the rear
limb and flexors of the trunk carry the whole body forward with

308 PLAYS, GAMES AND SPORTS

all the force at their command. Instead of trying to gain the
utmost speed and then ceasing at the finish as when one releases a
thrown ball or loses contact with the shot, the boxer makes his
strongest effort of arm, trunk and leg muscles just as the fist comes
in contact with the opponent or the bag. The reaction of the blow
helps in recovering, requiring no muscular action to regain balance
as in throwing unless the boxer fails to strike squarely; when he
"hits the air" the extensors of the forward limb and trunk must
act with promptness and force to keep him from falling.

Serving. — In serving with a tennis racket the arm movement
can be effectively reinforced by both the forward inclination and
the rotary movement of the body. The best position to take in
preparation for serving is with the racket arm turned away from
the net nearly 90 degrees, so as to use the crosswise movement of
the arm that utilizes the best action of the pectoralis major, after
the manner of shot putters. This position also makes a full turn
of the body possible in the movement (Fig. 80). As the racket
swings toward the ball the body rotates on its axis by action of the
oblique trunk muscles and rotators of the hips, assisted by a down-
ward swing of the free arm; at the same time the body leans for-
ward, due to contraction of the abdominal muscles and the exten-
sors of the rear limb. When the ball is struck the blow has the
momentum of the whole body behind it.

The server in tennis gets one advantage from the sharp forward
inclination of the body not realized by the thrower or the boxer.
His next move is to run forward into the court, and the position
at the end of serving launches him well into his run, so that he does
not, like the boxer, have to limit the slant and the power of the
stroke for fear of falling.

Success as a tennis player depends much on agility in covering
court, which means action of all the muscles of the trunk and lower
limbs in great variety, and on ability to put speed on the ball,
which means reinforcement of the arm by the momentum of the
body in every play. In forehand drives the muscles rotating the
trunk to left act while in backhand strokes it is the opposite set;
work for the abdominal muscles is present in both. In quick play
the free arm has so much work in maintaining balance and in help-
ing to give the rotary movement that it is really left unused less
than is generally assumed.

Batting. — Batting in baseball illustrates again a reinforcement of
an arm movement by forward inclination of the body on the feet
and its rotation about a central axis. A right-handed batter stands
with his left side toward the pitcher, body inclined and trunk and
hips twisted to right, bat held well around to right. At the proper
time in the pitcher's " wind-up" he steps toward the pitcher with

PLAYS, GAMES AND SPORTS 309

his left foot and increases the flexion of his right knee, which makes
him incline still more strongly away from the pitcher, and increases
a little more the twist of trunk. As the ball approaches he leans
toward it by extending his right knee and flexing his left one, swings
his bat toward the ball by extension of elbows, sideward swing of
arms and twisting of trunk and hips to left. When the bat hits the
ball the body should be in motion to carry the bat toward it with
both its leaning and its rotating movement, thus giving it the
combined momentum of bat, arms and body. Batters readily learn
the arm movement and the rotation but many of them fail after
years of practice to lean toward the pitcher during the swing.
This fault is increased by fear of being hit by the pitched
ball.

The strokes used in hockey, lacrosse, golf, polo, and other sports
differ in detail from those just explained but all of them will on
careful observation be seen to consist essentially of the three
parts — arm swing, forward movement of the body on the feet and
its rotation on its vertical axis.

Kicking. — Kicking a football consists fundamentally of flexion
of the hip and extension of the knee of the same side at once — a
movement that can be made by action of the rectus femoris alone.
In the mildest kick this may be all that is necessary.

To strengthen the movement we may use all the extensors of the
knee and all the flexors of the hip that do not interfere with exten-
sion of the knee. This eliminates only the sartorius. The ham-
string group must be relaxed, for its action would prevent both
movements.

The unsupported side of the pelvis must be held up to the level
of the other side, which will require the lesser glutei of the support-
ing side. The whole body weight must be supported by the sup-
porting limb, requiring action of the extensors of hip, knee and
ankle. The front side of the pelvis must be held up firmly to sus-
tain the pull of the hip flexors; the hamstrings of the supporting
side will do this.

If the kicking leg is to be raised as high and with as much force
as possible, the pelvis must be flexed on the trunk. This cannot
be done because of the iliofemoral ligament unless the supporting
knee is flexed; when this knee is flexed a little the abdominal muscles
can lift the front of the pelvis. In this case the weight is thrown
so far backward that the arms must be raised up and forward to
keep the balance, which brings in the arm-raising group.

The strongest kick of the ball that one can make requires then
the strong action of the extensors of both knees, with the support-
ing knee slightly bent; strong flexion of the hip on the kicking side;
strong work of the ankle extensors and hip abductors and extensors

310

PLAYS, GAMES AND SPORTS

of the supporting side; moderate action of the abdominal muscles
and the arm-raising group.

This is the style of kick made by goal keepers in soccer in a kick-
out and by players in the Rugby type of game in the kick-off. A
drop-kick requires the same form of kick without the high lift of
the leg.

Fig. 187. — Punting the football. (Photo by Underwood and Underwood.)

In punting and in advancing the ball in soccer the kick is given
with the inside of the foot just in front of the instep, the whole
limb being rotated outward in the hip. This position and a side
sweep of the foot that is used brings in the adductors of both sides,
in addition to the muscles named before. The abductors of the
foot are also active.

Locomotion. — Locomotion, as seen in games and sports, includes
walking, running, hurdling, jumping, vaulting, climbing, rowing,
paddling and bicycling.

Walking, as used in play activities, has no special features beyond
what has already been explained. Running in general is the same

PLAYS, GAMES AND SPORTS

311

as that considered in Chapter IX except the crouching start and
the swing of the arms used in sprint racing.

In the crouching start (Fig. 188) the trunk is horizontal, the arms
helping a little in supporting the weight but mostly in keeping the
poise. The hip and knee of the rear limb are flexed to a right angle
and those of the other limb still more. The spine is arched.

All this puts considerable tension on the extensor muscles of the
trunk and lower limbs and also puts the gluteus maximus in a
position to help. No other position yet discovered enables the
runner to start so quickly.

In sprinting the rotation of hips and shoulders is eliminated as
far as possible in the belief that they interfere with the runner's
speed. The arms are held straight down at the sides and care is

Fig. 188. — The crouching start.

taken to swing them directly forward and backward, so that they
will not produce any rotary movement of the shoulders. The trunk
muscles are all kept in static contraction to give strongest sup-
port for the vigorous action of the muscles moving the limbs. This
stops the breathing, most sprinters running the 100 yards with
but two or three breaths and some with but one.

Skating differs from running in several particulars. The body is
supported on the skates practically all of the time, progress being
made by a sliding motion instead of a flight through the air.
Because of the nature of the skate and its contact with the ice or
floor the advancing movement is diagonally forward and sideward, so
that the limbs are rotated outward, largely eliminating the extensors
of the ankle from the work. The trunk is held nearly horizontal

312

PLAYS, GAMES AND SPORTS

to avoid wind pressure, and this puts the pelvis in good position
for all the extensors of the hip to act, including the gluteus maxi-
mus. The main work is done by the extensors of the hip and knee,
supported by the erector spinse. The extensors of the ankle finish
the stroke and the flexors of the lower limb bring the limb forward.
In hurdling the runner has to spring up into the air to pass an
obstacle at regular distances. He avoids the hurdle by his upward
spring and by the position of the limbs as he passes it. One of his
problems is to so combine these two movements as to save the
most force.

Fig. 189.— Taking the low hurdle.

The spring employs the same muscles that are being used in the
run, giving a stronger contraction in this particular step. In going
over a hurdle the front limb is held well forward by the flexors of
the hip and the knee is flexed about to a right angle by relaxation
of the extensors, the pull of the hamstrings as the hip is flexed
giving the slight force that is needed. In this position of flexed
hip and knee an outward rotation of the hip, produced by the six
outward rotators, lifts the foot easily and to a sufficient height.
The sartorious is peculiarly adapted to help in this combination of
flexion and outward rotation of hip and flexion of knee.

PLA YS, GAMES AND SPORTS 313

The rear limb is made to avoid the hurdle by holding it far to
the rear and flexing the knee as it passes over the obstacle. This is
accomplished by inclining the body sharply forward to permit the
backward slant of the thigh and by continuing the action of the
hamstring group after the spring is completed, these muscles
extending the hip and flexing the knee at the same time. Notice
the position of the arms as they are held up by the arm-raising
muscles and moved forward or backward to assist in balancing by
the action of different parts of the deltoid and by the pectoral or
infraspinatus.

Of the various forms of jump in games and sports the standing
broad is the easiest to analyze because both sides of the body work
in unison. The movement begins by a passive flexion of trunk and
lower limbs and a backward swing of the arms; then the whole
body leans forward and just as it begins to fall forward the extensor
muscles of the trunk and limbs contract suddenly, projecting the
body into the air in a forward direction.

As the extension begins the arms are quickly swung forward by
the arm-raising group, including the pectorals, and just after the
feet leave the ground the arms swing quickly down again by action
of the arm depressors, especially the latissimus. The upward
momentum of the arms, gained while the feet are still on the ground,
is used to help in lifting the whole body. The effect is more marked
when weights are held in the hands and still more so when the hands
rest on a fixed support, as in vaulting. The distance gained by
the movement of the arms is not great but a fraction of an inch
may win a contest and is always worth gaining.

After the violent extension by which the spring is made and while
the body is in the air there is a general flexion of trunk and limbs,
not made with any purpose or even consciously. It is probably
caused by a recoil from the strong extension, the flexor muscles
being put on a stretch as the spring is made and shortening like an
elastic cord when the extensors relax.

Before the feet strike the ground the joints are nearly straight-
ened again by a mild contraction of the extensors, and when they
reach the ground there is another passive flexion, the extensor
muscles undergoing a lengthening contraction to ease the jar; after
reaching partial flexion the body straightens to erect position by
continued action of the same muscles.

The running broad jump differs but slightly in mechanism from
the standing broad. The momentum of the run carries the body
farther even if the height is no greater. The running jump is usually
said to be taken from one foot, but this is scarcely true, for while
the feet are not together at the time of the spring and they do not
leave the ground at exactly the same time, they both take part in

314 PLAYS, GAMES AND SPORTS

the spring and apparently they work all the more effectively by
extension of the limbs in quick succession rather than in unison.

In the standing high jump the jumper stands with his side toward
the bar and begins by a slight passive flexion as in the other jumps ;
the limb nearest the bar is then thrown strongly upward by the
flexors of the hip and the abdominal muscles, the other limb still
being flexed somewhat; this is quickly followed by a spring from
the other foot, using the extensors of the trunk and limb. The
arms aid in the movement by swinging in practically the same
manner as in the standing broad. A slight inclination toward the
bar, made without any considerable effort as the first limb is raised,
gives the jump its sideward trend. The pelvis is flexed on the
trunk by a forcible contraction of the abdominal muscles as the
flexors of each limb act to lift the limb over the bar.

The running high jump is made in several ways but in two main
styles: the scissors form, which closely imitates the standing high,
and the straight jump, in which the jumper runs in a direction
at right angles to the bar.

The scissors jump, taken with a run lengthwise of the bar, is too
much like the standing jump to need a separate analysis.

When one who jumps from the left foot makes the straight form
of jump he runs squarely at the bar and extends the limbs in rapid
succession, the right one first. As the left limb is being extended
the right is being lifted by the flexors of the hip and the whole
body is thus turned to the left on the left toe as a pivot. The
turn thus begun continues while the body is in the air and the
jumper passes the bar with his left side or face toward it, according
to the force of the turn, and alights facing the starting-point.

In all forms of vaulting the main work of lifting the body is done
by the extensors of the trunk and limbs, as in the jumps. The
arms aid more or less by supporting a part of the weight so that
the jump does not have to lift the whole of it.

In the vault with the pole there is a considerable gain in the height
over that of the jump, partly because the arms help to lift the body
and partly because the momentum of the run and the jump is
applied to a lever that shifts the direction of the force and turns a
horizontal motion into a circular one.

The jump is practically the same as that used in high jumping.
The body is at first suspended by the arms in nearly a passive man-
ner, the hand flexors being the only muscles in strong action. As
the body nears the bar the trunk and limbs are lifted by contrac-
tion of the flexors of all the joints and the arm depressors and then
extended to the position shown in Fig. 190 by the extensors. The
hands hold to the pole long enough for the body to clear the bar
and for the feet to begin the downward movement due to gravity,

PLAYS, GAMES AND SPORTS

315

then drop it with a push that will vary in force with the exact
position of the body and the pole. On alighting the extensor
muscles of trunk and limbs come into action to lessen the jar by
a lengthening contraction, followed by a shortening contraction to
bring the body to erect posture unless the balance is lost.

Mountain climbing is essentially like walking up stairs, using the
flexors of the limbs to lift the feet and the extensors of trunk and
limbs to lift the body, the complete flexion giving the gluteus
maximus a chance to help. In going down the mountain the
weight is lowered at each step by a lengthening contraction of the

■- ">Taij

■i ,

•*-.*>

iSB^*

-^J§S»

Fig. 190.— The vault with the pole.

extensor muscles. There is much turning and bending that varies
the work of the trunk muscles and brings all of them into action a
part of the time.

Climbing the rope or pole, using both hands and feet, starts by
grasping it with the hands, using the flexor group. Then the feet
are lifted by action of the flexors of the trunk and limbs and the
whole body may be lifted at the same time with arm depressors
and flexors of the elbow. The rope is now grasped by the feet,
using the adductors of both thighs and the flexors of one limb
acting against the extensors of the other; then the hands are moved

316 PLAYS, GAMES AND SPORTS

up the rope by use of the arm-raising muscles and the extensors of
the trunk and hips, after which the movement is repeated.

In practically all forms of swimming the body is propelled along
or through the water by the use of the arm depressors and the
extensors of the lower limbs. There are a few exceptions — the
flexors of one hip being used in the scissors kick and the adductors
of the thighs in the breast stroke. When the arm depressors are
not used on opposite sides of the body at once, as in the side strokes
and the crawl, they are reinforced by the trunk muscles of the same
side.

The arms are returned to position for the stroke by the arm-
raising muscles and the limbs by the flexors except in the scissors
kick, where the hip extensors of one side are used. This work is of
course milder than that of the propelling muscles.

Rowing is a typical pull of the arms alternated with a combina-
tion of push and arm depression. The pull is aided by extension
of the trunk and lower limbs and the push by flexion of the same
joints. The push may also be accompanied by flexion of the wrists
to feather the oar.

Paddling is a complex one-sided movement. In paddling on the
right side the arms are moved downward to the right, using the
latissimus and teres major of the right arm and the pectoral of the
left, reinforced by the rhomboid of the right and the serratus of
the left side and the right internal and the left external oblique
muscles.

Bicycling employs the extensors of the lower limbs in alterna-
tion, the action being supported by the extensors of the trunk.
The extension of the trunk is reinforced in turn by a pull of the
arms on the handle bars. The flexion of the limbs may be brought
about by allowing them to rest on the pedals, but that will waste
force.

In order to secure the greatest speed in bicycling the rider leans
far forward and lowers his arms, since this puts a tension on the
trunk muscles, giving them more power, and also puts the gluteus
maximus in position to work powerfully through more of the circle.
Instead of simply pushing down on the pedals he follows each
pedal and pushes it with his foot as much of the way around as
possible. With toe clips to attach the foot to the pedal the work
can continue practically all the way around the circle, the extensors
acting to push part of the way and the flexors acting to pull it
around during the balance of the revolution. This uses the flexors
as well as the extensors in the work and there is another advantage —
the force used is not limited by the weight of the body as it is in the
simple downward push. One limb flexing and the other extending
reinforce each other, requiring less action of the trunk and arms
for this purpose. There is probably no bodily mechanism capable

PLAYS, GAMES AND SPORTS

317

of exerting so much force per minute as this way of driving the
bicycle.

The position just described uses the extensors of the spine in
such an elongated position that it is bad for posture when taken

Fig. 191. — Bicycling, erect position. (Photo by Ethel Perrin.)

Fig. 192. — Bicycling, stooped position. (Photo by Ethel Perrin.)

too often or for too long a time. Since boys are apt to be more
interested in speed than in posture it is important to teach them
how to follow the pedal with the foot and to have their bicycles
equipped with toe clips, so that they can get the racer's speed
without his characteristic hump.

CHAPTER XVII.
INDUSTRIAL OCCUPATIONS.

The bodily movements involved in industrial occupations, like
those of play and sport, include both the handling of objects and
locomotion. In sport locomotion is perhaps the more prominent
of the two, but in industry the reverse is true. This has come about
because in the displacement of muscle by machinery it is the field
of locomotion that has been invaded most. While boats, steam
trains, trolley cars, automobiles and elevators now do most of the
transportation of people and freight — once done by muscular
power — many of the primitive ways of handling objects are still
in use and the use of machinery is leading to the invention of new
forms of movement.

Beginning with movements in which lifting and arm raising are
prominent features, handling brick will serve as an example of the
simplest type.

Handling brick is seen most often in the loading and unloading
of wagons and cars. It is done by picking them up in the hands,
two bricks at a time, and tossing the two to another workman
who catches them and places them in a pile. The work involves
the flexors of the hands and fingers, the arm-raising muscles and the
extensors of the trunk and limbs. The knees are flexed by some
workmen while others bend forward from the hips. Flexion of the
elbows by the biceps group is usually present. Each of the two
men has about the same amount of work and uses the same muscles
in nearly the same way.

Gathering beets, turnips, cabbages, and other vegetables and
pulling weeds are tasks of the farmer and gardner using practi-
cally the same bodily mechanism as handling brick. The stoop-
ing position of the body and the lifting bring in the extensors of
trunk and limbs, while pulling the plants from the soil requires
vigorous action of the hand flexors. Handling baskets and bags
of grain is very similar, with a one-sided action when the object
is shouldered. Picking strawberries and weeding onions and other
small plants, because of the stooping posture, give much work for
the extensors of trunk and limbs.

Baggage men, expressmen, and men who haul lumber, stone and
freight of all kinds have to grasp, lift, and in general use the bodily

INDUSTRIAL OCCUPATIONS

319

mechanisms just mentioned. Many other special examples will
occur to the reader.

Lifting and reaching upward is seen in hanging clothes on a
line. Women with weak arms are especially likely to hollow the
back and protrude the abdomen in this work, for reasons given
elsewhere.

Carrying hod is work for the extensors of the trunk and lower
limbs and for the middle trapezius and levator of the side holding
the hod. The workman is apt to flex his trunk laterally to avoid
putting the weight on the muscles of one side of the trunk, and this
is apt to induce lateral curvature unless the hod is carried on alter-
nate sides.

Fig. 193. — The action of the body in shoveling.

Shoveling is a more complex movement. When the material
moved is loose like sand or coal the shovel is loaded by pushing it
into the pile, using the triceps to extend the elbow and the arm-
raising group to support it. When the work calls for more force
these two groups increase their action and the abdominal muscles,
particularly on the side toward the shovel, act to aid them. The
entire weight of the body is brought to bear on the work by lean-

320 INDUSTRIAL OCCUPATIONS

ing forward and the rear limb helps by a push with its extensor
muscles.

The shovel and its load is lifted by the extensors of the spine
and hips, the arms remaining extended. The hand and arm nearer
the shovel bear the whole load, the other arm pushing down on the
upper end of the handle, using triceps and arm depressors. The
lifting arm is strongly supported by the trapezius and after it has
been raised 45 degrees, by the lower serratus.

The easiest way to move the loaded shovel horizontally is by a
rotation of the body on its vertical axis, the lifting muscles just
mentioned remaining in action during the swing. This brings in
the rotators inward of one hip and outward of the other, with the
rotators of the spine and a swing of the arms made by the pectoral
of one side and the latissimus of the other.

If the loaded shovel must be moved upward there must be
increased action of the lifting muscles, including those of the arms,
trunk and limbs. Usually the flexors of the elbows will be used at
the end of the movement; the pronators of one forearm and the
supinators of the other will empty the shovel.

Pitching hay or grain is a similar movement. It takes less force
to insert the fork and it can be tilted to vertical position of the
handle with the load still in place. If the load is to be moved hori-
zontally the action is the same as with the shovel. When it is to
be moved high overhead the fork is either lifted by raising the
arms or, if it is too heavy for that, tilted to upright position and
then lifted upward by an extension of the trunk and limbs. With
the fork handle upright it can be held close to the body, enabling
the arms to lift it more easily.

The study of work in which pushing is prominent may be begun
by using a lawn mower. The pushing mechanism of the arms,
already explained, is in vigorous use here but is for most of the
time in static contraction, the use of the limbs in walking giving
the motion and the extensor muscles of the limbs being the moving
muscles. The arms are supported by the abdominal muscles when
the trunk is erect or nearly so, but if the trunk is inclined forward
far enough this work is transferred to the extensors of the trunk.

The use of the wheelbarrow involves lifting combined with push-
ing. To begin work the workman flexes trunk and lower limbs and
grasps the handles, then lifts it to erect posture; to walk forward
while lifting the weight the extensors of the limbs must each in
turn bear the added weight of the barrow. If there is resistance to
the forward motion the pectorals, anterior deltoid and upper
serratus must act; work is thrown on the abdominal muscles and
the extensors of the trunk a little relieved by the backward trac-
tion on the shoulders. To balance the weight as nearly as possible

INDUSTRIAL OCCUPATIONS 321

on the spinal column and thus relieve both the flexor and extensor
muscles of the trunk the workman leans forward in going forward
or up hill and backward in going backward or down hill.

The combination of arm depression with pushing is found in
washing, using the old-fashioned washboard. The clothes are
rubbed up and down against the board by alternate flexion and
extension of the elbows, assisted by the arm elevators and depres-
sors and reinforced by flexion and extension of the trunk.

Fig. 194. — Action of the whole body in using the lawn mower.

Vigorous depression of the arms calls for contraction of the abdom-
inal muscles to reinforce the movement. The abdominal muscles
being relatively weaker in women than in men, women are more
apt to flex and extend the trunk in work of this kind by alternate
contraction and relaxation of the extensors of the hips and spine,
the body weight acting in place of the flexor group. The muscles
for arm depression act all of the time to press the clothing against
the board.

Ironing is another occupation that has depression of the arm as
a leading feature. The heavy iron gives much of the needed pressure
21

322 INDUSTRIAL OCCUPATIONS

by its weight, so that one arm can do the work. The usual aid is
given the arm muscles by action of the trunk muscles on the side
toward the iron.

Alternate flexion and extension of elbow aided by the usual
pushing and pulling muscles move the iron over, the goods. The
combined forward and backward motion with twisting of the whole
body that we have noticed in so many cases is useful here. Lifting
is also involved.

Sawing is a good example of pushing with one arm. The work
of the arm is reinforced by the rotators of the trunk and hips.
When the saw is pushed forward horizontally the abdominal
muscles are required, and if it is pushed vertically upward it is the
trunk extensors. Workmen prefer to have the piece that is to be
sawed placed horizontally and then it is easily held by placing one
knee upon it and the saw is pushed diagonally forward and down-
ward. This makes it possible to use the weight of the body to
reinforce the arm muscles and the extensors of the spine and hips
can be used to raise the trunk again each time.

Plastering is another kind of work that calls for lifting and push-
ing. The soft plaster is rubbed onto the wall with a flat trowel and
leveled and smoothed by rubbing the trowel against the surface
with considerable force. When the wall to which the plaster is
applied is overhead the triceps and arm-raising group, supported
by the extensors of the trunk and limbs, do the work. Sometimes
the workman leans backward, relieving the extensors of the trunk
and bringing the strain on the abdominal muscles. When it is a
side wall there is less elevation of the arms and more lateral pressure,
involving the abdominal group, particularly of the side toward the
wall.

The use of the carpenter's plane is much like ironing, but the
movement of the tool is more extended and more in a straight
line. Both arms can be used, bringing into action the extensors of
elbows, pectorals of right and latissimus of left, each with their
regular associates. The force and extent of movement is increased
by rotation of trunk and hips to left and forward inclination of the
body through the action of the flexors of the trunk and hips and
extensors of right knee.

A similar case is the use of the screw-driver. Here the work of
the arms, also explained in a former chapter, is supported by the
same muscles as in sawing as far as the pushing movement is con-
cerned, while the twisting movement brings into action various
muscles of the trunk and limbs, depending on the height and direc-
tion of the tool. Another is boring with bit and brace. Here all
the force at command is often needed to push endwise of the bit,
the limbs being braced and the trunk leaned far forward against

INDUSTRIAL OCCUPATIONS 323

the tool while the right arm makes the circular motion by suc-
cessive action of pectoral, deltoid, shoulder extensors and depres-
sors of the arm. Still another interesting example is boring with
an auger, in which a push of arms and body is combined with the
twisting of the tool by the arms. This twist is made by the biceps
group and pectorals supported by the upper serratus and the
flexors of the right side of the trunk.

Driving a fast horse will illustrate pulling movements. When it
is not necessary to pull very hard the arms do the work, supported
by the rhomboid and by the extensors of the trunk and hips. If
the pull must be stronger the arms remain straight and the pull is
made by the trunk and hip muscles, the extensors of the knees
possibly acting also.

The cross-cut saw is a long saw pulled by two workmen, one at
each end. This is a pull by one arm usually; both arms may be
used but even if they are the pull is one-sided. The rotators of the
trunk and hips are employed here as well as the extensors of the
trunk and limbs. The foot of the same side as the arm used is
placed to the rear; this favors twisting of the hips to. that side and
the extensors of the forward limb work in the pull.

The use of the pickaxe or mattock is a good example of striking
movements, using both arms at once and nearly in the same way.
The tool is swung high overhead by the arm-raising group and the
extensors of trunk and hips; then the arm-depressing muscles add
their force to the weight of the tool and the abdominal muscles
act to add to this the weight of the trunk. One foot is usually
advanced to make it easier to keep the balance. Driving post
with a sledge and chopping a log that lies flat are similar.

Chopping down a tree requires a diagonal stroke, down and side-
ward. The axe is raised over one shoulder and swings down and
across the body, combining the rotary action of the body with the
movement of flexion seen in the last examples.

Sharpening a stake with an axe held in one hand while the other
holds the stake gives the one-sided type of striking movement.
The striking muscles of the arm are here reinforced by the side
muscles of the trunk of the same side and by lifting the limb of
that side, so as to put most of the body weight into the blow.

Beating rugs with a carpet beater, driving nails with a hammer,
pumping water, and chopping with a hatchet are familiar uses of
the arm depressors and triceps of one side assisted by the flexors
of the trunk, especially of the same side, or by the weight of the
trunk brought in to reinforce the blow by sudden relaxation of
the extensor muscles. Both the weight of the trunk and the action
of the abdominal muscles are apt to be used.

Hoeing is especially interesting because it illustrates how the
muscular action and the posture of the body vary with the vigor

324

INDUSTRIAL OCCUPATIONS

of the work. The tool being light and being used in rather loose
soil or in mixing mortar it is not lifted high like the pick but is
moved up and down much more rapidly.

To make the hoe cut into the soil a blow is struck with varying
force according to the condition of the soil. In some cases the
weight of the hoe may be sufficient; then it is only necessary to
use the arm-raising muscles and extensors of the trunk and let the
tool fall; when a little more force is required the arm-depressing
muscles act; with a slightly increased hardness of soil the arm
depressors are reinforced by the abdominal muscles.

Fig. 195. — The action of the body in hoeing.

is lifted.

The extensors in action as the hoe

The gradual beginning of the action of the abdominal muscles
in cases of this kind can be easily noticed by placing one hand on
the table as the reader is seated and placing the other hand on the
abdominal muscles. Begin with a slight downward push against
the table and gradually increase it while feeling the condition of
tension of the abdominal group. They are lax at first and only
after a certain amount of arm depression is given do they begin
to contract, but with any more of the downward movement they
contract with each push of the arm.

INDUSTRIAL OCCUPATIONS

325

The strong and rapid contraction of the abdominal muscles in
hoeing soon begins to tire them and then the workman bends the
trijnk forward. The weight of the head and shoulders can rein-
force the arm depression if there is a sudden relaxation of the exten-
sors with each stroke. This makes.it unnecessary to use the abdom-
inal group but it soon becomes tiresome for the extensors, as they
have to hold the weight of the trunk in a stooped position for most
of the time and relax exactly with the stroke of the hoe. The result
is that the workman unconsciously assumes a more and more

Fig. 196.-

-The action of the body in hoeing. The flexors of the trunk acting as
the hoe strikes.

stooped posture until he becomes aware of it and that it is tiring
his back muscles; then he stands more erect until he forgets again.
Mowing grass with a scythe is a horizontal stroke with the arms
that must be supported by action of the rotators of the trunk and
hips. The tool is made to cut as it swings from right to left. The
arms are swung to left, shoulders twisted to left, right hip rotated
outward and left hip rotated inward; then the tool is lifted by the
arms and trunk and swung in the reverse direction above the level
of the cut grass.

326 INDUSTRIAL OCCUPATIONS

Sweeping with a broom is quite similar to mowing so far as the
work of the body is concerned, while the vertical position of the
broom handle makes the arm movement different. In sweeping
toward the left with the left hand uppermost both arms act cross-
wise of the body, as in turning an auger; pectorals, anterior del-
toid, upper serratus and flexors of elbows are in action. The arm
movement is aided by trunk and hips turning to left as in mowing.
The work of the body can be varied by sweeping the other way,
but the arm work is nearly the same.

Turning a crank that is hung upon a horizontal axis, as in various
farm, shop and household machinery, includes arm extension,
depression, flexion and elevation in turn, supported by the flexors
of the trunk in the first two movements and by the extensors in the
other two. The trunk work is more prominent on the side of the
active arm and the push and pull at the top and bottom of the turn
bring trunk twisting into it. The support needed by the arm can
often be supplied in part at least by use of the other arm, when a
solid object is near that can be grasped by the free hand. The work
of this arm is the reverse of that done in turning the crank.

When the crank is mounted on a vertical axis, as in some machines,
the elevation and depression of the arm is eliminated and a move-
ment sidewise and crosswise must be used. This is not so easily
done by the arm, partly because of the location of the arm muscles
but chiefly because the body weight cannot be used to reinforce
the arm movement. The horizontal push must be reinforced by
the abdominal muscles, the pull by the extensor group, and the
lateral movement by the rotators of the trunk, using both sets in
the two phases of the turn.

Walking is by far the most important type of locomotion in
industrial lines.

The farmer has much walking to do over soft and uneven ground,
the driving of team or stock occupying his attention meanwhile.
As a consequence he is apt to develop the habit of a long and
laborious stride that is not well suited to the smooth streets and
walks of the town, giving him a reputation among townsfolk for
awkwardness of gait.

The walking done by the man who drives the delivery wagon,
involving jumping on and off the wagon and running along smooth
walks and up the steps of dwellings gives him an elastic and graceful
step.

Much of the walking seen in industry is combined with lifting
and Carrying, adding the action of arm muscles and increasing the
work of the walking mechanism by the added weight.

Climbing in industrial occupations is most often the climbing of
stairs and ladders.

INDUSTRIAL OCCUPATIONS 327

Climbing stairs is one of the most violent of exercises, as to the
total amount of work done, for it requires a lift of the whole body
weight through many feet in a short time. It has been found that
going up stairs involves as much work as walking thirteen times
as far on a level place. Persons with well-developed extensors of
hip, knee and ankle usually go up stairs in an erect position, while
the old and weak incline the trunk forward, enabling the gluteus

Fig. 197. — Action of the whole body in climbing the ladder.

maximus to help. This of course adds much to the work of the
erector spinse and makes stair climbing a generally tiresome exer-
cise, but it is necessary with those who lack the strength of limb.
Climbing the ladder, common in the building trades and in spray-
ing trees and gathering fruit from them, involves more balancing
than climbing stairs, but when the hands are free they can be used
to help in lifting the body. Grasping, flexion of elbows, and arm
depression are the motions involved.

328 INDUSTRIAL OCCUPATIONS

QUESTIONS AND EXERCISES.

1. Explain the peculiarity of walk developed by practice on rough ground, Are
additional muscles- brought in when the surface is rough or is it only a change in the
way of using the same muscles?

2. What muscles are rested by changing hands in pitching grain?

3. A boy picking strawberries and another picking cherries change work. What
muscle groups are rested in each boy.

4. One shoveler throws the clay from a trench six feet deep while another throws
the same soil ten feet horizontally away from the trench. Is the difference mainly
in quantity of work or in location of work in certain muscle groups? What would
either gain by exchanging?

5. One workman dumps his wheelbarrow load sidewise while another dumps his
load directly forward over the wheel. Explain the difference in the muscle groups
employed.

6. What advantage is it to the washer-woman to haive the tub and board placed
below the level of her hips? Above it? What determines the best height for it in
any case?

7. Make a list of occupations that tend to develop uneven shoulders; incomplete
flexion of elbows; lateral obliquity of the pelvis; lack of the normal lumbar hollow
in the back.

8. Make a list of occupations that tend to develop especially erect posture and
carriage; strong feet and a springy gait; a strong back; strong abdominal muscles;
a full chest.

9. Which is the best exercise for a dentist: golf, bowling, rowing, boxing or
pulley weight exercises? For a postman? For a stenographer?

10. Why is one apt to hollow the back excessively in hanging up clothes? Explain
the mechanism of the movement and the advantage of leaning backward at the
waist.

BIBLIOGRAPHY.

Allis, Oscar H. : Man's Aptitude for Labor in the Upright Position, Trans. Coll.
Phys., Philadelphia, 1887, ix, 35.

Bakes, Frank: President's Address, Am. Assn. Adv. Sc, xxxix, 351.

Bancroft, Jessie H.: The Posture of School Children, New York, 1913.

Barwell, Richard: Lateral Curvature of the Spine, London, 1895.

Beevor, Charles E.: Muscular Movements and their Representation in the
Nervous System, London, 1904.

Bradford and Lovett: Orthopedic Surgery, New York, 1899.

Campbell, Harry: Respiratory Exercises, New York, 1904.

Chauveau, A. : Comparative Anatomy of the Domesticated Animals, New York,
1905.

Cunningham, D. J. : The Lumbar Curve in Man and the Apes, Nature, xxxiii, 378

Demeney, Georges: Mecanisme et Education des Mouvements, Paris, 1904.

Duchenne, G. B.: Physiologie des Mouvements, Paris, 1867.

Feiss: Mechanics of Lateral Curvature, Am. Jour. Orth. Surg., July, 1906.

Gerrish, F. H.: Text-book of Anatomy, Philadelphia, 1902.

Gray, Henry: Anatomy, New American edition, Philadelphia, 1913.

Haycraft, J. B. : Animal Mechanics, chapter in text-book of Physiology, edited
by E. A. Schafer, Edinburgh, 1900.

Hebert: L'Education Physique Raisonnee, Paris.

Howell, W. H.: Physiology, Philadelphia, 1914.

Hutchinson, Woods: Jour. Am. Med. Assn., September, 1897; May, 1903; British
Med. Jour., October 28, 1899.

Lombard, W. P.: The Action of Two-joint Muscles, Am. Phys. Ed. Rev., viii,
141; Am. Jour. Physiol., xx, 1.

Lovett, Robert W.: Lateral Curvature of the Spine and Round Shoulders,
Philadelphia, 1907.

McKenzie, R. Tait: Exercise in Education and Medicine, Philadelphia, 1909.

INDUSTRIAL OCCUPATIONS 329

McKenzie, R. Tait: The Isolation of Muscular Action, Am. Phys. Ed. Rev.
November, 1908.

McKenzie, R. Tait: The Legacy of the Samurai, Am. Phys. Ed. Rev., xi,
p. 215.

McKenzie, R. Tait: The Relation of Thoracic Type to Lung Capacity, Mon-
treal Med. Jour., April, 1904.

Mackenzie, William Colin: The Action of Muscles, New York, 1918.

Mollier, S.: Ueber die Statik und Mechanik des Menschlichen Schultergurtels
unter normalen und pathologischen Verhaltnissen, Jena, 1899.

Mosher, Eliza M.: Brooklyn Med. Jour., July, 1892. Int. Jr. Surgery, Feb. 1919.

Morris, Henry: Human Anatomy, Philadelphia, 1903.

Posse, Baron Nils: Special Kinesiology of Education Gymnastics, Boston, 1894.

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Regnault and Raoul: Comment on Marche, Paris.

Richer, Paul: Anatomie Artistique, Paris, 1890; Physiologie Artistique, Paris,
1896.

Schatz, W. J. : A Physical Exercise for the Correction of Lumbar Lordosis, New
York Med. Jour., April, 1892.

Sherrington, C. S.: The Integrative Action of the Nervous System, London,
1908.

Skarstrom, William: Kinesiology of Trunk, Shoulder and Hip, Springfield,
Mass., 1907; Gymnastic Teaching, Springfield, Mass., 1914. " ,

Wirt: Mechanics of the Ankle-joint, Mind and Body, iii, 125 and 145.

INDEX.

Abdominal exercises, 220
Abductor pollicis, 153
Acrobatic exercises, 274
Adductor brevis, 170
gracilis, 170
longus, 170
magnus, 171
pollicis, 153
American Posture League, 258
Angle of pull, 34
Archery, 135

Arm, depression of, 105, 282
elevation of, 98, 278
fundamental movements of, 97, 127
gymnastic movements, 108
parting, 112
raising backward, 1 13
forward, 111, 278
sideward, 109, 279
upward, 112, 280
Association of muscles to secure power,
268
skill, 274
speed, 272
neurones, 49

Baggagemen, 319

Balancing on one foot, 169, 285

Bancroft test for posture, 252

Basket ball, 133

Batting, 134, 308

Bibliography, 329

Biceps, in action, 121

arm, 119

thigh, 166
Bicycling, 316
Bones of foot, 187

of forearm, 138

parts of, 30
Boring with bit and brace, 323
Boxing, 128, 307
Bowling, 134, 300
Brachials, 123
Brachioradialis, 123
Breathing, 226

Breathing, movement of abdomen in,
234
of ribs in, 228
posture of shoulders and, 77

Chairs in relation to posture, 258
Chest, 226

enlargement of, in breathing, 228

firm, 79
Chinning the bar, 132
Chopping wood, 324
Clavicle, 59
Climbing rope, 132, 315

stairs and ladder, 327
Columns of the spinal cord, 52
Coracobrachialis, 91
Cross rest, 132
Cross-cut saw, 324
Crouching start, 311

Dancing, 290
Defects of foot, 198

of posture, 254
Deltoid, 84

in action, 85

isolated action, 86

loss of, 87
Diaphragm, 232
Dorsal interossei, 146
Draymen, 319
Driving horse, 324
Dynamometers, 25, 269

Elbow and forearm, 115
joint, 115

muscles acting on, 117
Erector spinae, 214

in action, 217
Expansion of abdomen in breathing,234
External intercostals, 228
oblique, 212

332

INDEX

External brevis pollicis, 150
carpi radialis brevis, 140
longus, 140
ulnaris, 141
communis digitorum, 144
Extensor longus digitorum, 191
pollicis, 150
ossis metarcarpi pollicis, 150
proprius hallucis, 191
Extensors of ankle in action, 181
of hip in action, 165
of knee in action, 181

Fall hanging, 292

Fallout, 288

Femur, 158

Fibula, 177

Fingers, muscles acting on, 142

Flat back, 261
foot, 199

Flexor brevis pollicis, 151
carpi radialis, 139

ulnaris, 140
longus pollicis, 151
ossis met. pollicis, 152
profundus digitorum, 142
sublimis digitorum, 142

Foot, bones of, 187
defects of, 198
muscles of sole, 198

Forearm, bones of, 138

Gastrocnemius, 192
Gathering vegetables and fruits, 319
Gluteus maximus, 163
medius, 168
minimus, 168
Graphic records of breathing move-
ments, 239 1
of posture, 253, 260, 262, 265
Gymnastic dancing, 290

movements of arms, 108
general kinesiology, 278
of trunk, 220

Hamberger's model, 230
Hand, 136

fundamental movements of, 154
Handling brick, 319
Handspring, 292
Handstand, 293
Hanging by hands, 131
Headspring, 296

Headstand, 296
Hernia, 265
Hip-joint, 155
Hod carrying, 320
Hoeing, 324
Humerus, 84
Hurdling, 312

Iliacus, 142

Iliofemoral band, 157

Industrial occupations, 319

Infraspinatus, 96

Inhibition, 53

Intercostal muscles, external, 228

internal, 228

theories of action of, 23 1
Internal oblique, 212
Interossei, 146
Ironing, 322

Joints, 30
Jumping, 313

Keynote position, 263

Kicking, 309

Kinesiology of gymnastic movements,

i ^278

Knee flexion while standing, 184

joint, 175
Kyphosis, 255

Lateral curvature of the spine, 261
Latissimus, 93

in action, 94
Leaning hang, 292

rest, 291
Levator, 68
Levers, 32
Lifting, 280

Lombard's paradox, 185
Lordosis, 259
Lower limb, 155

fundamental movements of,
201
Lumbricales, 146
Lungs and fallout, 288

Methods of studv, 28
Mobility of chest," 240

INDEX

333

Model to represent the two-joint

muscles of thigh, 182
Motor nerve cells, 45
endings, 46
Movements of elbow, forearm, wrist
and hand, 115
of foot, 189
of hip-joint, 155
of knee-joint, 175
of shoulder girdle, 59

joint, 82
of spinal column, 205
Mowing lawn, 321

with scythe, 326
Muscles acting on elbow-joint, 117
on fingers, 142
on foot, 190
on hip-joint, 158
on knee-joint, 177
on shoulder girdle, 62

joint, 82
on spinal column, 210, 212
on thumb, 150
on wrist, 139
construction of, 22
contraction of, 19
number of, 17
origin and insertion of, 20
of right leg, 193

palm, 146
of sole, 198
strength of, 22
structure of, 18
Muscular control, 40, 55
energy, source of, 17
tone, 21
work, 21

Neck, firm, 78
Nervous system, 42
Neurones, 40

Oblique extensors of spine, 216
Olecranon, 115, 117
Outward rotators of hip, 172

Paddling, 298
Palmar interossei, 146
Palmaris longus, 140
Parallelogram of forces, 35
Pectineus, 162
Pectoralis major, 88
in action, 90

Pectoralis minor, 75
Pelvic girdle, 155
Pelvis, position of, 248
Peroneus brevis, 197

longus, 194
Pickaxe, 324
Pitching ball, 300

hay, 321
Plantar ligaments, 188
Plastering, 323
Position of feet, 200
Posture, normal, 251

of shoulders, 77
Pronator quadratus, 124

teres, 124
Prone falling, 291
Psoas, 158
Pulling, 127
Pushing, 127, 283

lawn mower, 321

Quadratus lumborum, 217

Reading and posture, 256
Rectus abdominis, 211

femoris, 161
Reflexes, 48
Rhomboid, 70

Robert's "chopping" exercise, 224
Rolls, forward and backward, 293
Rotation of hip-joints in batting, 308

in boxing, 307

in hammer throw, 295

in throwing, 300

in walking, 173
Rowing, 132, 316

Sacral angle, 248
Sartorius, 160
Sawing, 323
Scaleni, 235
Scapula, 59
Scoliosis, 262
Screw-driver, 323
Semimembranosus, 167
Semitendinosus, 166
Sensory nerve endings, 47

neurones, 46
Serratus magnus, 71

posticus inferior, 238
superior, 236
Serving in tennis, 134, 308
Shot put, 134, 303

334

INDEX

Shoulder girdle, 51

joint, 82

extension of, 107
flexion of, 108
muscles acting on, 83
section through, 83
Shoulders, firm, 129

posture of, 77
Shoveling, 320
Side, falling, 292

holding, 292
Skating, 311
Soleus, 192
Spinal column, 305

curves of, 307

cord, 42

ganglion, 44

nerves, 43
Spirometer, 241
Splenius, 213
Sternocleidomastoid, 234
Strength of muscles, 22
Stride positions, 287
Striking, 128, 306
Subclavius, 96
Subscapularis, 97
Summersaults, 295, 296
Supinator, 125
Supporting muscles, 271
Supraspinatus, 88
Sweeping, 327
Swimming, 316
Synapse, 48

Table of sines, 39

Team work among muscles, 267

Tensor, 163

Teres major, 95

minor, 96
Throwing, 128, 300

Tibia, 177

Tibialis, anterior, 190

posterior, 196
Tossing, 300
Transversalis, 237
Trapezius, 62

in action, 67

lacking, 65, 66
Triceps, 117

in action, 118
Trunk, 305

bending of, 218

fundamental movements of, 218

gymnastic movements of, 218
Tumbling, 293
Turning a crank, 327
Two-joint muscles, 182

Uneven shoulders, exercises for, 80
Upright position, 245, 284

Vastus externus, 188
intermedius, 189
internus, 189
Vaulting, 314
Vertebra;, 206
Visceroptosis, 264
Volley ball, 134, 306

Walking, 201, 327
Washing, 322
Wheelbarrow, 321
Wrist, muscles acting on, 139

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